LOPE-C 2012

Thin transparent layers on polymer films are used to drastically enhance the permeation barrier properties of polymer films while at the same time maintaining the flexibility and optical transparency of the polymer substrates. Applications range from food packaging films to encapsulation films for solar cells or flexible electronics. Very low water vapor and oxygen transmission rates are required for the encapsulation of flexible OPVs and OLEDs. This paper introduces a technology for manufacturing ultra-high permeation barrier films using roll-to-roll coating processes. It is based on reactively sputtered oxide barrier layers and an interlayer of inorganic-organic hybrid polymers (ORMOCER®s). The multilayer barrier is compared to other high barrier technologies and evaluated regarding barrier performance, optical transparency, process stability and productivity. The water vapor transmission rate (WVTR) has been measured using different methods for different sample sizes and test conditions. The measurement limit of a MOCON Aquatran system (5•10-4 g/(m²d)) has been reached with a three layer stack at 38°C / 90% relative humidity. The technology is now being used for a pilot production of barrier films. In addition to the barrier layers, further layers can be applied to the polymer film, e.g. layers to provide a mechanical protection, a smoothing layer for further processing or transparent conductive layers for manufacturing of flexible organic solar cells or flexible OLEDs. Different applications e.g. using the barrier film either as a substrate for organic electronic devices or for the encapsulation of such devices will be discussed.

Currently there is a trend to develop printed electronic products for different kind of applications. Most of printed products will be integrated devices combining parts, components and/or building blocks (BB) which partly utilise printing technologies but also other conventional technologies. Therefore, there will be a need for a combination of production processes which can be fully roll-to- roll (R2R) but also more like pick&place on a moving continuous WEB. The printed products are composed of different BBs such as main backplane onto which modules like control electronics, lighting, PVs and batteries will be assembled. The aim is to combine component attachment/lamination, printing (screen and inkjet), bonding and encapsulation to integrate different functionalities on a flexible foil, and to transfer developed approaches to a roll-to-roll platform. In this work the feasibility of adapting different production methods to R2R environment and experimental results on backplane printing and integrating different modules onto the backplane are presented. Various methods and materials for making the backplane and for BBs mechanical attachment and electrical contacting are described. Rotary screen printed silver metallized substrates (PET and PEN, thicknesses 150 µm and 50 µm)) with a daisy chain test structure are used to study the interconnections between the foils. This allowed the measurement of the resistance of the whole Daisy chain or the resistances of two individual interconnections. For interconnection materials anisotropically conductive adhesive films, anisotropically conductive pastes and isotropically conductive adhesives from different manufactures were employed. As the bonding method hot bar bonding or oven curing were used, the experimental procedure being compatible with the suggestions of the materials supplier. Thermal humidity testing at 60oC/95%RH and thermal cycling between -40….+85oC were used as the environmental tests for the test structures. Based on the test results materials for system manufacturing were selected.

Children’s books containing interactive elements between the reader and the book are one growing market of the printing industry. If the interaction is based on electronics, normally conventional “silicon” technology is applied. In 2011 a student group of the University of Applied Sciences Munich developed the interactive book “Ducky in the Dark” containing 9 different interactive elements. These elements are based on printed electronic compounds of the OE-A toolbox stocked by OE-A members. Printed solar cells, RFID and batteries are used for the power supply of these interactive elements, based on OLED, electrochromic and electroluminescent displays, conductive lines, buttons, isolators and capacitors. The book “Ducky in the Dark” demonstrates the state of the art of interactive elements based on printed electronic compounds. In the beginning the development focused on the technical feasibility to fulfill the target market requirements. Economic or legislative issues were considered rudimentarily. According to economic and legislative issues the book had to be optimized. A second student group worked in an optimization project with the objectives - to analyze materials and productions costs, - to evaluate customer requirements and - to check the conformity to statutory provisions, industrial standards and regulations. Next to the analysis interactive elements were optimized as well as new ones developed. The project group discussed their results with publishers of children books and could concretize the market requirements for printed electronic components in children’s books. By using the quality management tool “House of Quality”, the market requirements could be matched to the interactive elements as well as to the printed electronic components. Hence there is a systematically researched platform for designing and developing new children’s books with interactive elements based on printed electronic components fulfilling the technical, economical and legal requirements of the customers.

RFID is fast growing technology and has the potential of replacing barcodes. The passive RFID tags, consist of a radio transceiver chip with attached antenna. The tags are placed onto objects, allowing remote identification by magnetic or electromagnetic fields depended on operation frequency. In many wireless systems like RFID, cost effective antennas are highly desired. This can be achieved using conducting ink and appropriate mass production printing technology. In this paper, an overview of antenna design for passive HF and UHF RFID tags is presented. The studies is focused on presentation of various requirements of such designs for two practical applications: the UHF RFID tag for box tracking in logistics and the HF RFID tag for newspaper tracking in retail trade. An antenna design for both applications is described and its various practical aspects, such as sensitivity to fabrication process are also analysed. The antennas were printed with screen printed CRSN2442 SunTronic Silver 280, thermal drying silver conductive ink. Monofilament polyester plain weave meshes with three densities were applied. As printing substrate coated cardboard and uncoated recycled paper were used. Drying conditions were varied to obtain good print quality on both printing substrates. The print quality such as print uniformity, line’s gain and wicking were evaluated mainly by image analysis with different input devices (digital optical microscope and scanner). The analysed influences, of drying conditions and meshes density on the print quality of printed conductive layer, were proved to be significant. For both antennas full measurement characterizations were performed. For practical aspect of applications adhesiveness and abrasiveness of printed conductive layer were also analysed. Beside this optical and mechanical degradation of recycled paper and cardboard were evaluated after drying at required temperature, which differ from those recommended by the producer.

Traditional printing (gravure, inkjet, flexography, rotary screen) has attracted as a methodology of a mass manufacturing of printed electronics to reduce the production cost. But due to the limitation of each printing method, it is hard to manufacture ‘all roll-to-roll printed electronics’ such as OTFT. High operating velocity is the strong point of the direct roll printing (gravure, flexography, etc). But its resolution of printed line and registration is lower than inkjet printing. On the other hand, the resolution of inkjet printing is very high, but its productivity is lower than roll printing. Thus the inkjet printing has been used only for the feasibility test of printed functionalities so far. Hybrid printing technology which is combination of direct and indirect printing methods is an alternative methodology to meet the productivity and resolution of printed functionalities. For example, combination of gravure and inkjet printing is a completed setup for ‘full R2R printed electronics: large-area printing achieved by gravure, and top layer printed by inkjet printing with high resolution. High resolution of registration should be achieved for the adaption of R2R printing technology for the printed electronics. Register error of a moving substrate is defined in two printing rollers as the relative difference of the distance between the previous printed pattern by the upstream printing roller and the printed pattern in the downstream printing roller.In this research, a mathematical modeling of the hybrid register is derived using the equation of mass equilibrium. The indirect printing section was converted as a noncontact roll printing to derive the mathematical model. Parameter sensitivity analysis was carried out with varying span length, operating velocity, and tension disturbance. This mathematical model will be used for the development of hybrid register controller.

Many works have been focused on fabrication of transparent conductive film (TCF) in order to replace an ITO film, as there is a high demand in adding flexibility into electronic devices. Besides the flexibility in the devices, a large-scale production is also one of key issues for the purpose of cost-down. For the flexibility issue, carbon nanotubes (CNTs) is a good candidate while the printed electronics is one for the second. This study is related to develop a novel method how to fabricate a TCF using CNT via printed electronics. A CNT is a peculiar conducting material due to one dimensionality in its conductivity. When it is applied to fabrication of conducting films, the geometric factor should be considered. Roll-to-roll (R2R) continuous printing is an attractive technology for mass-producing flexible printed electronics such as TCF. Especially, R2R based slot die coating is one of the preferred methods when high precision is required. Originally, transparency and sheet resistance of TCF are dependent on characteristics of material and bare-substrate, respectively. In this study, however, we found the correlation between geometric qualities and major parameters of R2R slot die coating systems. It means that functional qualities such as transparency and sheet resistance could be controlled by system parameters such as coating speed, coating gap, ink flow rate and operating tension because the functional qualities are very sensitive to thicknesses of coated layers. The possibility and feasibility of R2R based slot die coating for TCF using CNT are confirmed.

The presentation demonstrates possibilities automatic optical inspection and measurement systems (AOI systems) provide for inline control and optimization of thin film coating processes (R2R metrology). Modern AOI systems apply new methods for the evaluation of coating properties, while standard optical process control systems monitor coating properties by measuring only a few spots on the material. In the latter case this is done with a significant time delay after the production of the material. Modern AOI systems monitor the homogeneity of coating properties and return their absolute measurement values for the full material width in-line. Such systems are mainly based on typical AOI system components, such as digital line cameras and LED line illumination, allowing • evaluation of small local irregularities, such as pinholes, scratches, particles, .…, and • monitoring of the homogeneity of layer properties (i.e. thickness, surface structure, transmittance/reflectivity) for the full width of the material. Both kinds of measurement (local defects and material property measurement) use the same cameras, making the system more compact and less expensive. The modern AOI systems can be complemented by specialized in-line measurement systems. They enable calibration of the output, which is gathered by the cameras and interpreted by the electronic evaluation systems. This finally provides the capability to report absolute values of coating properties over the full width of the plastic film immediately following the coating process. Furthermore, instant feedback of the measured values into the production process makes it possible to keep it within the defined process window. As an example for this solution a traversing measurement head applied to a TCO coating process is presented. It measures in-line TCO layer properties, such as layer thickness, surface topology (i.e. haze) and layer resistivity. Main advantage of modern AOI systems is more reliable data collection during the manufacturing process allowing faster correction and leading to a more efficient production.

Current studies lively focused on the flexible and transparent display. To deal with this kind of display, one of the compulsory technologies is required to make a transparent and flexible conductive film beforehand. A study about coating of CNT(Carbon Nano Tube) solution on the plastic film(for example, PET) has been reported. The coating thickness and roughness is important factors affecting sheet resistance and transparency of conductive film). On the other hand, R2R slot-die coating systems are used for making coating layer on the plastic film. In R2R systems, operating tension is considerably important because of following phenomenon. Too low operating tension causes slip between web and roll. Slip can cause lateral motion error and it produces register error. Too high operating tension make possibility of plastic deformation of web. Moreover, operating tension of the R2R slot-die systems make change of surface angle between coating solution and web surface. This change is related to surface energy of web. In This paper, investigation of relationship among operating tension of the R2R slot-die coating systems and coating thickness and roughness was performed in experimental way. Experimental result showed coating thickness and roughness are inversely proportional to the operating tension. An explanation of this phenomenon was described using the tension-contact angle relation ship. Also, novel method to decide optimal operating tension in the R2R slot-die coating system is presented.

Roll-to-roll(R2R) continuous process is rising as the solution for mass production of printed electronics. It is reported that various printing(coating) techniques such as gravure printing, slot-die coating and screen printing are applied for fabricating OPV. Web accumulator is an apparatus to maintain operating speed at the processing zone while changing unwinding and winding reel and is consist of multiple idle rolls and the accumulator carriage. Owing to having multiple rolls in the accumulator, the printed(coated) surface should contact with idle rolls in the accumulator and is expected to have surface defects like scratch. In this case, an air-flotation apparatus such as air-turn bar could be considered as an alternative of idle roll. Air-cushion between web and the air-turn bar prevents web is scratched from undesired contact but excessive tension causes touch-down of web. So moderate operating condition should be studied to prevent touch-down. In this paper, a mathematical model of the accumulator including air-turn bar was derived. The mathematical model is consist of the accumulator carriage model, the tension model in accumulator considering air layer thickness change, and the driven roll model. Open-loop response and frequency response of the system was also analysed using developed model. A design guideline for the non-contact transporting web accumulator was suggested.

Organic electronics can be produced by either evaporation in vacuum or liquid processes like printing. Regarding speed and cost of production, the latter has the potential of being highly efficient. Unfortunately, solution processing is affected by many different kinds of instabilities. Especially when using small molecules, a major problem is the sequential processing of different semiconducting layers on top of each other. Not only the wettability but also the solubility of the materials has to be taken into account. Interdiffusion effects may inhibit the formation of defined interfaces resulting in mixed layers that can greatly diminish device performance. For the optimization of the solution process it is important to determine the thickness of the mixed region. Indirect measurements, for instance of the efficiency of the device, may not be reliable as they can be influenced by many different effects. Layer-by-layer XPS analysis is possible, but extremely time consuming and difficult to apply. We propose impedance spectroscopy as a fast and simple method for the detection of mixed layers. The electric characteristics of every semiconducting layer can be described by an equivalent circuit consisting of a resistor and a capacitor in parallel. Therefore, a diffusion free multi-layer can be represented by multiple of such RC elements in series. If a mixed region is present at the interface, this approximation is not valid anymore. This leads to a detectable change in the impedance spectrum of the multi-layer and can be related to the degree of inter-mixing.

The potential for combining flexography with bathless electroplating has been demonstrated reel to reel for the production of high conductivity grids. Conductive grids are required to increase conductivity over large areas for transparent conductors such as PEDOT for large area lighting with OLEDSs and Photovoltaics. A large degree of transparency is needed and therefore low area coverage is required for the tracks that make up the grid. However, the key quality characteristics of the grid are the conductivity and consistency of the tracks. Grids orientated at 90° to the print direction have been flexographically printed at 4m/min to produce 200m of printed material. The grids of 50µm and 100µm track width have nominal area coverage of 1.75% and 3.5% respectively and were printed using a banded anilox to vary ink volume transfer across the 450mm print width. The printed material was then electroplated in a reel to reel process to deposit metallic copper onto the printed silver grids. The surface topography of the samples printed onto polypropylene substrate was measured before and after electroplating. Changes in track profile and roughness have been determined with a focus on consistency between rows and at the knuckle where tracks meet. The conductivity of the grids has been measured in both directions. A high degree of consistency is seen between the tracks in the print direction and those at 90° to the print direction. Low area coverage is achieved with a high conductivity showing that these technologies can be integrated to produce continuous R2R highly conductive transparent features.

Block copolymers (BCPs) have become of great interest for high-resolution patterning because of their easy synthesis, controlable block size and high solubility in solvents. BCPs show different phase seperation depending on their fraction of blocks. This feature allows obtaining desired shape, geometry and lenght of nanopatterns. Such nanopatterns supply optimum contact area at p-n junction interface and lead to increase in performance. On the other hand, BCPs are promising materials also for large area printed electronics. In this study, we demonstrate nanopatterning of colloidal nanocrystals for devices. Colloidal Cadmium calgogenite nanocrystals were synthesized as water or organic soluble. Different molecular weight or fractioned PS-PMMA BCPs were used as template for nanopatterns.. Phase seperation of Nanocrystal/BCP blends are influenced by the molecular weight and fraction of BCPs. Figure 1 shows the schematic wiev of nanopatterned devices.

The ability to rapidly reproduce accurate and precise conductive micro-scale networks is crucial for the development of large-area printed electronics. In this paper, the flexographic printing process has been employed for the deposition of micro-scale conductive networks. The printed networks have been utilised to reduce the sheet resistance of a PEDOT:PSS coated transparent conductive layer on a flexible substrate, for enhanced thin film conductivity. Through specific improvements, the limitations of the process were resolved achieving excellent accuracy & consistency of the conductive tracks. High resolution conductive tracks were printed, achieving a standard deviation of 2 μm for a width of 68 μm over a large area R2R continuous production runs. Surface morphology analysis showed the printed tracks presenting a uniform smooth convex shape, overcoming the side-edges built-up typical of classic flexography and presenting an optimum structure for successive depositions. The printed networks allowed achieving a sheet resistance of 3 Ohm/sq at 7% area coverage.

Several materials are under development in order to improve the efficiency of solar cells, focusing in that which can be printed. Luminescent solar concentrators are usually used with down shifting materials for increasing the photon flux incoming to the PV device. At Leitat Technological Center, Eu based ink was developed to this purpose [1]. The organolanthanide complex, Eu(tta)3phen, already used in OLED [2], can be evaporated and prepared as photoluminescent ink. As down shifter, the Eu complex absorbs in UV range and emits at visible light, present high stability under ageing accelerated test and can be use also as UV protection thin film. The Eu based ink was formulated in order to use in screen printing technology. Different concentrations of Eu(tta)3phen was used in the formulation of screen printing inks. Viscosity and surface tension of the ink was adapted for screen printing and the printed substrate by using specific resins, solvents, rheology modifiers, and other additives.

Printed thick film electroluminescent lamps on paper have a number of a number of potential advantages over conventional ITO based lamps in terms of enhanced customer experience, cost, appearance and processability. Placing lamps on opaque substrate requires a reverse build architecture and the printing of a transparent conductive material as the upper electrode. In order to investigate the performance of the lamps, lamps were printed on 4 opaque substrates using a top emission architecture with PEDOT:PSS being used as the transparent conductor. The performance was compared to lamps based on a traditional ITO based bottom emission lamps. Lamp output was around 50% of the output of the ITO based lamps and could be attributed to a number of factors. The dominant reason for the lower output is the higher resistance and lower transparency of the PEDOT:PSS material used compared to the ITO. The architecture of the top emission EL lamps also leads to a reduction in lamp output as the phosphor particles provide a topological barrier to the production of a consistent coherent film and the net dielectric thickness is larger reducing the capacitance of the lamp. The increased resistive load of the PEDOT:PSS also limited the area of the lamps which could be produced while maintaining light output. The paper surface substrate played only a minor part in determining the lamp output with more absorbent substrates reducing output by around 10% compared to the non absorbent surface. The study shows that lamps can be printed on a wider variety of paper substrates, but that there is a trade off in output compared to ITO based lamps. The discrepancy in output cannot be eliminated entirely by more conductive / less transparent PEDOT:PSS formulations.

Polyimide films are the most suitable substrates for use in printed electronics owing to their high thermal stability. However, high wettability of polyimide films by low viscosity inks produces excessive spreading of ink and result in forming uneven inkjet-printed lines with splashed and wavy-shaped edges. Moreover, when low viscosity inks are inkjet-printed on these films, coffee ring effect frequently occurred. This effect is caused by convection flow, during which nanoparticles segregate at the line edge. As previously reported, it makes low conductivity, especially if line width is below 400 m. The most obvious methods to prevent these disadvantages are by decreasing a surface energy of substrate or increasing a viscosity of ink. However, high viscosity ink is difficult to inject through an inkjet-printer, surface modification has been known for a practical way. In this study, we aim to inkjet-print well-defined, narrow (width < 100 m), and low electrical resistance lines with low viscosity silver nanoparticle ink on polyimide films. Optimal ink-receptive layer was formed on their surface. Lines 70 m in width with sharp edges were produced on the optimal substrate. On the other hand, the ink spread laterally on the polyimide film and result in lines with various widths 80-90 m. Moreover, the electrical resistance of lines on polyimide film (24 Ω) is threefold higher than that on optimal substrate (8 Ω) due to coffee ring effect. The coating layer brought out substantial improvement of line morphology and conductivity is because the coating layer absorbed ink solvent, thereby ink viscosity was raised. It effectively prevented a spreading and a convection flow of ink. This novel approach would contribute to the future of printed electronics because this technique enables ink viscosity to increase without modification of ink composition.

Recently, inkjet printing has been increasingly important for the emerging printable electronics on a variety of substrates, being flexible and/or stretchable, to dramatically reduce the material waste and the production cost. Some of the main problems in inkjet-printed patterns are the feature resolution and the pattern fidelity intrinsic to the fluidity as well as the incompatibility of an ink material. The surface modification by different morphologies or self-assembled patterns is known to enable the ink material to remain in narrow areas on a glass or a silicon substrate. In this paper, we report on a drop-on-demand (DOD) inkjet printing, directed by the topography on an elastomeric substrate, for producing conductive patterns with the feature resolution of a few micrometers. The underlying mechanism for the spreading and drying of ink drops in the topographic compartments can be understood in the two-dimensional parameter space of the geometric factors and the contact angle of the ink on the substrate. The ink morphology in such parameter space provides at least a first principle of the DOD inkjet printing. A groove structure with a rectangular cross-section of h in height and w in width, giving the aspect ratio of x=h/w, is produced on an elastomeric substrate of polydimethylsiloxane (PDMS) and a silver nanoparticle suspension is used as the ink material whose contact angle θ ≈55 degs on the PDMS. Above a certain critical value of xc ≈0.35, the ink drop is found to become globally stable and to fill the groove by the front propagation while below xc, the ink drop is split into two parts in contact with two side walls of the groove due to the liquid instability. This work was supported by the National Research Foundation of Korea under the Ministry of Education, Science and Technology of Korea through the Grant 2011-0028422.

Electrical interfaces and contacts are important features of printed electronic devices. In numerous applications, interconnections between the printed part of an electronic circuit and the conventional electronic devices are still required.
Classically, such contacts are achieved by soldering. However, this method has specific properties which are difficult to integrate in a printed electronics production process. This applies to newly develop printed strain gauge sensors in particular. Not all printed elements can be mechanically and electrically connected due to the very thin conductive layers, which are typical for printed electronics circuits and mostly incompatible with the properties of molten soldering alloy. This fact causes that the other improvement potentials by the printed strain gauge are not applicable.
To simplify the integration of printed electronics, we investigated a possible method for contacting thin functional layers. For this purpose, contact pads of pure copper foil were hot stamped and then overprinted. Since the contact pads are made of pure copper, a contact can be soldered on them in a further step, without attacking or destroying the functional layers. To test the functionality of components approached with such a method after overprinting, optical and electrical measurements were carried out after the production.

Electrode patterning using fast and cost-effective roll-to-roll (R2R) techniques has been one of the development aims at VTT. Two methods, namely lift-off and etching processes, were adapted to our R2R pilot printing machine to produce patterned silver, aluminium and indium tin oxide electrodes on polyethylene terephthalate (PET) substrate. Both methods are based on commercially available materials. The R2R lift-off process was used to pattern R2R evaporated Al and Ag electrodes on plastic substrates which were then applied for the manufacturing of Organic Field Effect Transistors (OFET). The patterned electrodes have sharp images and the image edges were straight. The lift-off process produced extremely smooth metal electrode surface and up to 7 times higher conductivity was obtained in comparison to printed metal electrodes. Currently, the minimum feature size of lift-off patterned metal electrodes is in the range of 40-50 µm. Etching process is based on screen printable paste etchant for patterning both metal and conductive oxides on glass and plastic. This method was used to pattern ITO electrodes for Organic Light Emitting Diodes (OLED) and Organic Solar Cells (OSC). ITO image edges were not as sharp as in the lift-off process but sufficiently sharp for the tested applications. Surface roughness as well as sheet resistance of patterned ITO electrodes remains the same as in the initial ITO. The minimum feature size in etching process was in the range of 125-200 µm depending on the ITO material and screen used in the rotary silk screen unit. One of the advantages of paste etching as compared to the more commonly used wet etching or lift-off processes is its user-friendliness as open containers of corrosive acids or organic solvents are avoided.

According to the information technology trend toward flexible and transparent electronic devices, needs for nano-sized devices are increasing. Organic nanowires (ONWs), the most representative 1-D nano-structure, possess many attractive properties for application to the future electronics. There are published several methods for preparing ONWs. However, they have some problems to be solved; orientation, positioning, etc. We realized the highly aligned ONW arrays by using an electrohydrodynamic (E-) nozzle printer which contains the precision linear motor stage. We successfully fabricated the aligned patterns of poly(9-vinylcarbazole) (PVK) nanowires using E-nozzle printing with the pitch of 50 μm and the diameter of 290 nm. To fabricate the 15 meters of PVK nanowire, it takes only 2 minutes. By doping the PVK nanowire with emitting dopants, we achieved well-aligned, multi-colored nanowires array due to the Förster energy transfer between PVK and the emitting dopants. We also applied the E-nozzle printing to fabricate the highly aligned nanowire field-effect transistors (FETs) based on poly(3-hexylthiopehene): poly(ethyleneoxide) (P3HT:PEO) blend (80:20, w/w) which showed a high mobility of 0.0148 cm2/V•s. To reduce the operating voltage of ONW FET, solid polymer electrolytes (ion-gel) consisting of an ionic liquid and triblock copolymer were used for the gate dielectric material. Using ion-gel dielectric, We achieved an extremely high average field-effect mobility of 3.2 cm2•V-1•s-1 in nano-channel transistors based on a single-stranded polymer nanowire. Our strategy to print the ONWs and fabricate their devices in precisely controlled manner can be one of most promising approaches for realizing flexible or textile electronics in large area.

Recently roll-to-roll gravure printing process has been increasingly considered for manufacturing a variety of electronics due to its characteristics like low cost, large area and mass production. The performance of printed electronics depends mainly on geometrical and morphological printed layer such as thickness and surface roughness. Gaining control over ink transfer in a roll to roll gravure system plays important role to determine the thickness of the electronic printed pattern. It is believed that NIP pressure has an effect on ink transfer in a roll to roll gravure printing system. However, few studies were reported the effect of NIP roll on ink transfer. In this study, analytical approach was suggested to investigate the effect of geometry and hardness of NIP rubber layer on average pressure. Furthermore, the effect of average pressure on ink transfer was demonstrated by simulation of deformation of plastic web in contact area. The high average pressure i.e. high hardness and thin rubber layer allow gaining a higher ink transfer. This work presents a guide line to choose NIP roller in roll to roll gravure printing system.

More than 2,000 years ago, a Chinese Cai Lun invited paper using micro-sized plant fibers. From the invention, it has been used as writing and printing substrates in our daily life. With developments of electronic technology, however, heavy and fragile glass has been used as substrates in some devices such as televisions, computers, and mobile phones. And then, light and flexible plastics are expected to be used as substrates in the future printed electronics. In 2009, we re-invited paper using nano-sized plants fibers. We call it optically transparent “nanofiber paper”. The revolutionary nanofiber paper has high thermal stability and optical transparency of glass, maintaining high foldability of conventional paper. Recently, we have developed printing technology of conductive patterns on the nanofiber paper using silver nanowires and then succeeded in some applications such as printed antenna or transparent onductive electrodes. In this presentation, we would like to introduce these achievements and also discuss the advantages of nanofiber paper in printed electronics.

The DMP inkjet system we examined here is often used for functional printing of thin films and smart structures like strain gauges, OLEDs or OFETs. In this case, the difference in drop volume, drop velocity or drop form in inkjet printing leads to errors in the printed films, and the functionality of the printed layers and printed devices is affected. The aim of this work is to determine the deviation of the drop formation parameters to minimize the errors in the printed layers and to improve the functionality of the printed structures. In the present work, the stability and reproducibility of the droplet formation in inkjet printing were investigated. We examined drop form, drop volume and drop velocity by using an external optical system with a high speed camera. The analysis of the droplet formation parameters was performed with a special analysis software. We compared the deviation of droplet velocity, drop volume and drop form. The stability of the droplet formation was tested on one nozzle to compare the drop volume, drop velocity and the drop form independently of the ink channel form variations in the print head. The reproducibility test was performed on the different nozzles, and parameters like drop volume and drop velocity were compared. This allowed us to consider the deviation of the optical system, the analysis program and the driving waveform.

Charge transport and mobility in organic semiconductors is strongly dependent on morphology features of the printed/coated layer. The crystallinity of the layer, the distribution of impurities and electronic trap states is crucially dependent on printing or coating parameters, on the drying process, and on the pretreatment of the substrate. Optimizing the printing process for a specific OFET layout and semiconductor material, one commonly intends to maximize the effective charge carrier mobility, as is determined using standard electrical transistor models. Unfortunately, mobility is not a very specific parameter from the printer’s point of view. An unexpected deficiency in charge carrier mobility in a printed semiconductor layer may have a plethora of possible reasons, and it is not always possible to identify the underlying issue. Testing dynamic OFET features such as the electric noise distribution can give valuable supplementary information which is intrinsically related to layer morphology in the molecular level. We present a quite easy to handle noise measurement technique which can essentially be integrated in the recording procedure for static OFET characteristics. The power distribution of the noise spectrum can usually be assigned to a power law, with an exponent that is highly specific for the charge carrier transport and trap distribution. The presentation shows a typical measurement circuit and the recorded noise spectra, and gives a physical interpretation.

Recently, much research efforts on flexible OLEDs as the next generation display and lighting have been devoted. Since the efficiency and lifetime of flexible OLEDs can be significantly affected by the penetrated moisture and oxygen, thin film encapsulation technology is crucial for the flexible OLEDs. In this presentation, we present a hybrid organic-inorganic multilayer moisture barrier with a very low water vapor transmission rate (WVTR) less than 10-6 g•m2/day. The organic layer is an optimized Al2O3/ZrO2 nanolaminate and the inorganic layer is a plasma polymer synthesized with hexamethyldisiloxane (HMDSO) vapor in a vacuum chamber. It has been known that the nanolaminates of Al2O3 and ZrO2 show much higher moisture permeation resistance than the single oxide layers. We will discuss the effect of nanolaminate on the moisture permeation in detail in this presentation. Also, we have optimized the nanolaminate structure to have the lowest WVTR with the smallest thickness. For the organic layer, HMDSO-based plasma-polymer layers are synthesized on the nanolaminate surface with various thicknesses. The effect of the polymer thickness on the bending property of flexible OLEDs will be discussed in this presentation. There are a number of advantages of the HMDSO-based plasma polymer, which are the high growth rate, the very low surface roughness, and the compatibility to the oxide nanolaminate. For the precise measurement of the WVTR, we have utilized the electrical Ca test. All the Ca test measurements have been carried out in the temperature of 85oC and the relative humidity of 85% for the accelerated tests.

We report our technology for the fabrication of solution processed roll to roll organic thin film transistors (OTFTs). Planarized transparent PEN foil is used as substrate for gate layer with copper structured by photolithographic process. Slit coating is used for coating the dielectric on the substrate and UV light source for the cross-linking. Vias are developed by the plasma etching method in roll to roll. µ-dispensing is used for deposition of the organic semiconductor solution hence opening the way of organic CMOS in roll to roll technology. Source and drain contacts are realized by screen printing of carbon paste. Characteristics and performance parameters of OTFTs will also be shown.

Flexographic printing is considered to be attractive for printed electronics because of the flexibility of the printing forms and their economically efficient production. However, the solvent compatibility of these printing forms may be a major issue. The solvents in functional fluids could trigger off a swelling of flexographic printing plates. Swelling of printing forms leads to an increase in volume and a change in the material properties. This can influence the quality and electrical properties of a printed layer. In this research, we analyze the swelling of fine structures of photopolymeric and elastomeric flexographic printing plates when exposed to solvents. We investigated various printing plates in combination with several solvents regarding the swelling of line width over a period of time, also examining evaporation. Furthermore, we studied whether swelling behavior differs with varying line width. Based on coherence between swelling and line width, the swelling of different flexographic printing plates could be considered when authoring the plate layout. By taking into account the time factor, we get an overview of time dependent swelling behavior and thus a tool to predict the life span of printing plates used with proper and improper solvents. In addition, the use of inappropriate solvents also affects the dissolving of material from flexographic printing plates. Dissolved materials migrate into the printed layer and thus affect the functionality of printed electronic components. To examine the dissolution of material during swelling we performed swelling tests and measured material loss. This phenomenon could have a direct influence on the quality and conductivity of the printed layer.

Large Area Printing processes such as gravure and flexo printing are highly efficient core processes for the economic fabrication of organic electronic devices like OFETs and OLEDs. However there are limitations due to oxygen and humidity in the atmosphere in which printing machines are usually operated. In these cases printing can lead to devices with lower performance, as compared to devices made by vacuum deposition techniques. This is not necessarily a result of the printing process itself but of the air influence on the material. This paper presents a combined flexo and gravure printing machine, which can be integrated in a glovebox production process and protects the substrate and printed film from harmful atmospheric influence. The substrate is guided by a feeder box via a housed printing unit to the delivery box. For the gas exchange in the printing unit an inlet for the desired atmosphere and an outlet for the used atmosphere is used. The substrate is mounted to a transport-shuttle in the feeder box. This can either be done in a glovebox under the usage of the well-controlled glovebox atmosphere or outside with a subsequent gas exchange in the feeder box. The shuttle is pushed into the printing nip and during the actual printing process transported to the delivery box. Both boxes are fixed airtight to the printing chamber and sealed against unwanted gas exchange by an air lock system. The printed sample can be taken from the delivery box inside a glovebox for further processing. So it is possible to integrate printing processes in an established and well known glovebox process and to combine printing processes like gravure and flexo printing with spincoating or vacuum deposition processes. The advantage is to compare a device completely produced by vacuum deposition with a partly printed device.

Bulky and rigid silicon solar cells with power conversion efficiency above 10% and a lifetime of 25 years have become the benchmark in photovoltaic industry. However, there are plenty of scopes for disposable and inexpensive solar cells with a moderate efficiency and a shorter lifetime, which can be compared with plant leaves with a typical efficiency of 2-7% and a lifetime less than a year. Our printed paper photovoltaics (3PV) is a step to achieve this objective (publish online on 14th Sept 2011 in Adv. Eng. Mat.). Our solar cell is free from expensive indium-tin-oxide and does not employ any vacuum process. We used only three roll-to-roll printing steps to print the complete solar cells under normal room conditions. Naturally oxidized zinc film, printed by transfer printing on paper, acts as cathode. Photoactive layer is a bulk hetrojunction of polymer/fullerene, printed by gravure printing. Poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS), printed by flexographic printing, acts as transparent anode. Our report demonstrates free patterning of all the three functional layers by gravure and flexographic printing techniques. The advantage of free patterning of all these layers is that it eliminates any extra process required to interconnect solar cells into a solar module. Despite the high surface roughness of paper substrate, our 3PV cells show a power conversion efficiency of 1.3% under an illumination level of 60 mW/cm2 and yield open-circuit voltage and short-circuit current density of 0.59 V and 3.6 mA/cm2, respectively. A paper substrate has several advantages, since it is inexpensive, eco-friendly, bio-degradable, easily recyclable, mechanically flexible and compatible with well-established printing processes. The solar cells can be recycled together with aluminum-coated food packages by the existing recycling systems. Our 3PV can start a new concept of use-and-throw solar cells.

Bearing in mind the shortage of fossil fuels and therewith the energy problem, new concepts and materials with higher energy efficiencies have to be developed. Organic light emitting diodes (OLEDs) are considered to hold one answer to the problem of more efficient lighting. So far, usually iridium(III)-, osmium(II)- and platinum(II)-complexes were used as phosphorescent emitters, which can theoretically reach electroluminescence quantum yields of almost 100%, for OLED applications. In contrast to these cost intensive metals, copper presents a cheap and easily accessible alternative and offers a new opportunity to develop blue emitting materials. Copper(I)-complexes with a d10 electronic configuration lack unoccupied low-lying metal-d-orbitals, which can quench emission, i.e. dd*-quenching does not occur. Furthermore a new emission principle, so-called “Singlet Harvesting“, was ascribed to copper(I)-complexes. In transition metal complexes with small spin-orbit coupling and small singlet-triplet splitting, e.g. copper(I)-complexes, fluorescence occurs from an excited singlet state so that a blue-shift of the emission maximum is observed. Additionally, by using fluorescence as the main radiative pathway, this new emission system shows short emission decay times which are crucial for the efficiency of an OLED at high current flow. Many examples of luminescent copper(I)-complexes containing imine and phosphine ligands are known so far. In order to energetically favor the complexation behavior as well as to stiffen the complex structure and therefore enhance the quantum yields, chelating ligands are used. In this project various luminescent, mononuclear copper(I)-complexes where the central metal atom forms a tetrahedral or trigonal planar structure were developed and synthesized. The synthesized complexes will be examined on their photophysical properties to gain new knowledge about the structure, stability and luminescence behavior. The photoluminescence properties of these copper(I)-complexes cover the visible spectrum in the range of 450 nm to 540 nm with quantum yields up to 75%.

SU-8 photo-imageable epoxy has become an integral material in the development and manufacturing of organic electronics and emerging displays. The SU-8 layer is used in the Organic-TFT backplane as an inter-layer dielectric and in the front plane for separation and containment of emerging front plane media. As these technologies rapidly transition from development to full scale manufacturing it is necessary to back integrate their process steps into established manufacturing equipment. A g-line sensitive SU-8 formulation has been prepared to enable integration of SU-8 into established production processes which utilize g-line type steppers. In addition, sensitivity to new LED sourced exposure tools was also investigated to demonstrate compatibility with next generation roll to roll exposure systems. The material showed an excellent process window with low Eo doses at 0.5 to 5 um film thickness range. Lithographically, the material demonstrated an excellent aspect ratio. The profiles exhibited straight sidewalls with good clearing between features. Material attributes of cross-link density, surface energy, volume resistivity and adhesion to typical substrates were compared with standard SU-8 exposed on a broadband toolset.

Printed electronic components fabricated on flexible materials may be subjected to bending stress during their life-time depending on the application environment. It is essential to be aware of the consequences caused by bending stress on electrical behavior of the component in order to evaluate their usability for such scenarios. In this study printed wiring components are continuously exposed to bending stress causing the structures to bend repeatedly from flat to curvilinear state. The study clarifies the influence of cyclic bending loadings on the line long-term electrical performance i.e. conductivity. In addition the effect of geometrical properties on the component reliability is evaluated based on the continuous cycling tests. Two different printing processes, ink-jet and silk screen, are used to fabricate the components under test. The components in this study are traces with total length of 65 mm containing two adjacent lines (25 mm) and the connecting line perpendicular to these (15 mm). The trace width is varied from 125 μm to 2000 μm and the thickness from single layer print to multilayer prints. All components are fabricated on a 125 μm thick flexible polyethylene terephthalate (PET) substrate using silver as the conductive material. The bending reliability tests are running and the results are reported in the final article. At this point it is already observed that the resistance of traces is increasing as a function of bending cycles. This indicates degradation in the conductive material due to cyclic bending as the mechanical stress is directed to the adjacent lines. Scanning electron microscopy (SEM) analysis supports this statement, showing clearly cracks in silver conductor. The reliability analysis for traces, with 20 % resistance increase as failure criteria, is presented for both printing technologies with variable line widths and thicknesses.

Much attention has been paid to the surface modification of an indium tin oxide (ITO) electrode by assembling functional small molecules via chemical linkages. It is well known that the organosilane can be used as molecular bridge for linking specific functional groups onto many solid substrates including silicon, aluminum oxide, and indium tin oxide. Thus, the 3-Chloropropyltrimethoxysilane (CPTS) was employed as molecular bridge linking onto the thin ITO film in our experiments. Herein, modification of ITO thin films with surface attachment chemistry has been studied. Firstly, ITO films are pretreated in order to activate the surface further by creating a greater density of hydroxyl groups. The activated ITO surface is modified secondly with silane coupling agent CPTS, to establish an organized self assembled monolayer anchored onto the film surface and subsequently salen complex which covalently binds to the silane anchor. Characterization of the surfaces utilizing techniques like contact angle, atomic force microscopy, scanning electrochemical microscopy and cyclic voltammetry is also reported.

Nowadays, we can see a strong effort in seeking for highly performing materials for cheap organic electronics. Together with the high performance of the materials, the usual second requirement is their high photo- and thermal- stability. Therefore a several tens of soluble derivatives of diketopyrrolopyrroles (DPPs) were prepared and investigated with respect to their molecular structure. Novel derivatives of DPPs and PCs with different side groups were synthesized to increase their solubility. Simultaneously, groups with various electron donating or withdrawing ability were linked to the basic pyrrolinone core to improve some of their optical and electrical properties such as absorption molar coefficient, conductivity, photogeneration yield and others. Thermal and thermooxidative stability was studied by thermal gravimetry and differential scanning calorimetry in either nitrogen or air. Relationship between the molecular structure of DPPs and Pcs, organic thin film morphology and their optical and optoelectronic properties such as charge transport and photogeneration were studied. The experimental characterizations were accompanied with quantum chemical calculations. It was shown, that depending on the side groups substitution, studied materials exhibit high molar absorption coefficient as well as high quantum yield of fluorescence or significant quantum yield of photogeneration. Some derivatives exhibit gas sensing properties. In spite of the fact, that most of the derivatives exhibit hole conductivity, the derivatives with significant electron conductivity were prepared recently in our labs. These properties together with chemical, light and thermal stability and reasonable solubility predestines them as potential candidates for printed electronics and optical applications. This work was supported by Ministry of Industry and Trade of the Czech Republic project No FR-TI1/144 and Grant Agency of the Czech Republic project No. P205/10/2280 and by project "Centre for Materials Research at FCH BUT" No. CZ.1.05/2.1.00/01.0012 supported by ERDF and IGA Brno University of Technology via FCH/FEKT-S-11-2 project.

When organic electronic devices are brought into contact with the environment, oxygen and water vapour will permeate into them and cause a degradation of their components. The encapsulation of the devices with flexible barrier materials containing alternating inorganic and organic layers provides their protection against these substances. In order to design encapsulation materials with further improved barrier properties, a deeper understanding of the permeation mechanisms arising in these structures is required. Based on experimental results, a model of periodically distributed defects within an impermeable or permeable inorganic matrix is established. The numerical solution of the corresponding diffusion equations results in the stationary and transient permeation rates for these structures. This shows how the permeation rates are influenced by geometric and material parameters of the barrier structures. The permeation through multilayer films is described by approximate formulas which are derived from the numerical results. They allow to represent a barrier structure as a combination of serial and parallel connections of permeation resistances. Furthermore the simulation results are compared to the results of analytic calculations and experimental permeation measurements. In the case of oxygen permeation through two inorganic layers separated by an organic layer, a reduction of the stationary transmission rate is obtained in simulation when the organic layer thickness is decreased. However, this tortuous path effect is significant only for very low thicknesses. Therefore it cannot completely explain the high barrier values measured for ultrabarrier films. It will be shown that in addition to the stationary permeation resistance also the permeation time lag contributes to the barrier properties of multilayer films. This relates to the question whether stationary or transient permeation is relevant in the application of encapsulation materials and in permeation measurement, e.g. in the calcium test.

The material and device quality of organic electronics are now beginning to mature to the extent that performance limitations and degradation are controlled by defects and traps. The defects and traps are extremely sensitive to processing routes and fabrication conditions specifically since different substrates and techniques of deposition are being tried out. However, unlike inorganic crystalline semicondcutors, tools to recognize electrically and optically sensitive trap states are not understood to the extent that they can be recognized and controlled. In this paper, we use time analyzed transient spectroscopy (TATS), a technique equivalent to deep level transient spectroscopy (DLTS) in time domain, to monitor trap occupation and carrier dynamics in high quality diodes based on MEH-PPV and Alq3 as prototypical materials. A charge transient measurement system based on current integration and with a facility to pulse the device under study is used to monitor carrier emission and capture. We show that the nature of non-exponential transients arising due to continuous state distribution of defect states can be easily monitored using this technique. The emission transients are stretched exponentials with a stretching parameter lying between 0.70-0.77 indicating the degree of spread in energy of the traps. The occupation of traps as function of duration of capture i.e. pulse filling time is studied for the first time giving insights into the role of these defects. We show that trap occupation grows as square root of filling time, and discuss the possible origin of this behavior. Evidence of charge redistribution among several bands of defects is also demonstrated.

Over the last decade magnetic materials have been extensively investigated due to their novel chemical, physical, and electronic properties, and the potential for their use in electronics [1-3]. In this study, we reported synthesis of Fe3O4 magnetic nanoparticles (MNPs) based on two phase method at low temperature. XRD, MFM, ESR, and TEM techniques were used for characterization. We also used MFM technique to analyze magnetic feature of thin films consisting of MNPs. Thin films were prepared as pristine Polystyrene and magnetic nanoparticle doped polymer films. Particle size of MNPs depends on reaction temperature and varied between 5-10 nm.

Much attention has been paid to the surface modification of an indium tin oxide (ITO) electrode by assembling functional small molecules via chemical linkages. It is well known that the polyelectrolytes can be used as monolayer for linking specific functional groups onto many solid substrates including silicon, aluminum oxide, and indium tin oxide. Thus, the poly (allylamine hydrochloride), PAH, and poly(styrene sulfonate), PSS were employed as molecular bridge linking onto the thin ITO film in our experiments. Herein, modification of ITO thin films with surface attachment chemistry has been studied. Firstly, ITO films are pretreated in order to activate the surface further by creating a greater density of hydroxyl groups. The activated ITO surface is modified secondly with negatively and positively charged polyelectrolytes to establish a stable layer which is charged positively and subsequently albumin molecule which electrostatically binds to the charged surface. Characterization of the surfaces utilizing techniques like contact angle, atomic force microscopy, scanning electrochemical microscopy and cyclic voltammetry is also reported.

In the context of today’s tremendous and ubiquitous research effort aimed to the field of organic electronics, a large area is opened up for the investigation of heterostructures combining the inorganic and organic materials, potentially offering cheaper and mechanically flexible alternatives to well established rigid electronic platforms or even entirely new and unique applications. One common crucial problem being in the spotlight of both the applied device engineering as well as fundamental research represents contact formation on metal-organic interfaces, since it plays a critical role in the performance of molecule-based electronics. Our work in this field is devoted to investigating electrical behaviour of metal-organic heterojunctions. Different contacting properties affecting charge injection and transport processes are desirable for the intentional formation of either injecting ohmic contacts or rectifying Schottky contacts. Among various different techniques for testing of contact qualities, we are closely focused on DC current-voltage measurements and AC impedance spectroscopy. These methods are relatively easily accessible and they give probably the most practical insight on the overall functional performance, directly utilizable in construction of more complex functional structures. The particular work being presented was based on electrical characterization of a modified PEDOT-class organic semiconductor contacted by several different types of metal electrodes. The test vehicles consisted of the organic layer deposited on the bottom electrode by simple spin- or drop-coating and formed to the final sandwich structure by sputtering of the top electrode. The analysis of experimentally obtained I-V characteristics and results of impedance spectroscopy was done in order to derive parameters characterizing the electrical properties of the metal-organic contacts under investigation. Phenomenological approach to assessing the stability and reproducibility of time- and voltage-dependent current responses was accompanied by discussion of some basic charge transport processes possibly governing the overall electrical performance of the studied heterogenous material systems.

The photovoltaic (PV) technology, up to date mainly focused on silicon based-solar cells, recently is significantly expanding its interest also in polymer solar cells (PSC) based on organic semiconductors. This class of materials permits to meet the electricity demand as well as offer secondary benefits such as the extension of the applications fields. Moreover, the solubility of the organic semiconductors and the processability at low temperatures allow their printability and, hence, the extension of the deposition methods for the fabrication of organic solar cells to printing technologies which guarantee high production rate and low costs. Among the various methods for printing functional materials for PV applications, the inkjet printing (IJP) technology is particularly suited to realize patterned structures allowing an efficient use of the materials. In the present work, we manufactured cells with bulk heterojunction (BHJ) structure, where the inkjet printed active layer was sandwiched between two electrodes. The active material was the regioregular poly(3-hexylthiophene) (P3HT):[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend and the cell stack was ITO/PEDOT:PSS/P3HT:PCBM/Ca/Al. As the active layer morphology plays a crucial role in determining the final device performances because it strongly influences the charge transport properties, we studied how the P3HT:PCBM morphology varies by varying the chemico-physical properties of the solvents. The film microstructure was optimized acting on the mixing ratios of the solvents and the printing parameters, such as drop emission frequency, drops overlapping degree and substrate temperature. The microstructure of the inkjet printed P3HT:PCBM films was analyzed by means of optical and morphological (AFM, SEM) analyses in order to correlate the improved electrical performances of the organic solar cells to the film morphology.

Since the first commercially successful applications for organic light-emitting diodes (OLEDs) have entered the lighting and display markets, new goals in the field of material development have arisen. For some time, researchers struggled in finding materials that can be operated with low turn-on voltages and high efficiencies, while having difficulties in fabricating air and moisture free test devices. Nowadays – with the introduction of iridium compounds and the development of advanced processing protocols – such problems can be successfully addressed. However, the manufacturing of long-time-stable multi-stack architectures is still challenging while the search for less pricey metals than irdium or platininum as emitting compounds is ongoing. Todays vacuum deposition techniques are unfavorable compared to solution processing due to the considerable expenditure when processing large devices. To put it in a nutshell: With a basic understanding on how an operative OLED can be build, the next goal is to construct it stable, rapidly and with low-cost materials. In this study, we demonstrate how the price of the materials and the stability of the devices can be adressed. Using a new class of copper(I) complexes as emitting materials, we present a strategy which enables both the direct tethering as well as cross-linking of luminescent copper complexes to host-polymers in one simple autocatalytic process without additional reagents, yielding an insoluble product with a well-defined structure. We were able to show that the emission band is not affected by our novel process while enhancing the structural stability. The presented technique opens the door to stabilized hybrid materials for OLEDs. We consider these results as a showcase reaction with can be applied to all copper(I) complexes to connect a basic system with variable functional units. Our approach may not only be used to simply demobilize an emitting complex, yet additionally to introduce charge transport-moieties in a modular fashion for OLEDs and/or donor/acceptor functionalities into organic photovoltaics.

A huge interesting progress in the field of organic electronic materials and devices has been observed in the last decade. However, the understanding of these materials is still a challenge to overcome. Most studies in literature focus on active devices such as OTFTs, OLEDs and OPVs. Nevertheless, a complete technology has to have also passive devices in order to allow the design of interesting applications and complex circuits. This paper deals with the development of a complete set of passive devices that allow the fabrication of simple applications such as filters or sensors. The process flow is a fully screen printed technology that uses exclusively organic materials on gold laser ablated flexible substrate. Discrete passive (R, L, C) devices have been processed and characterized. This has permitted the fabrication of RLC low-band pass filters that are dedicated to RF applications. Furthermore, based on these discrete passive components, we have developed a very high sensitive temperature sensor on Polyethylene Naphtalate (PEN) plastic substrate. We present the state of the art of our process development for RF applications using organic materials.

Organic Solar Cells are an attractive candidate for solar energy production. Their low production cost, processability, light weight and flexibility have attracted increasing interest on this technology. Nevertheless one of the main open issues with organic solar cells is the stability to environmental degradation. Different approaches have been proposed to overcome this problem, which can seriously impact the commercial applicability of this technology. Encapsulation with plastic barrier films appears to be the most viable solution, due to the ready availability of suitable barrier materials on the market; however their permeability to water vapour and oxygen is still high to guarantee the 5-years lifetime required for the final applications. Additionally, the cost of high-barrier plastics is very high. A different and potentially cheaper approach [1] consists in the use of inorganic thin films directly deposited on the top of the device for their encapsulation. These films can provide a good barrier to oxygen and water, and the barrier effect can further be increased simply by packaging the devices with cheap conventional plastic foils, thus allowing a good stability at low costs. In this work we have realized both P3HT:PCBM (polymeric) and DBP:C60 (low molecular weight) solar cells with either aluminium and silver cathodes, and we have used thin (25 nm) HfOx/AlOx films prepared by Atomic Layer Deposition (ALD) for encapsulating the samples. We have monitored the performances of devices exposed to air and kept in a nitrogen atmosphere and the results showed that the ALD deposited film enhances dramatically the stability of the polymer solar cells with aluminium cathode compared to untreated devices, although a constant loss of photovoltaic performance is observed upon ageing, while the devices stored under nitrogen keep their efficiency for over 1200 h. DBP:C60 solar cells, although less efficient, appear to be more stable than polymeric ones

Since C.W. Tang and S.A Van Slyke proposed their OLED in 1987 [1], these devices have become a very important field of research for displays and lighting. Nevertheless, OLEDs are very sensitive to moisture and Oxygen, which react with materials of devices and degrade their performances very quickly. Encapsulation and sealing alone are not sufficient to protect effectively OLEDs, so it is necessary to insert a desiccant (or getter) in the architecture of the devices [2] to capture the moisture and protect them. Without high performances hermetic sealants and getters, the lifetime of these devices is very limited and they cannot be used for any practical application. Using glass substrates, the permeability of the edge sealant is critical. Without getters, the ingress of water and Oxygen into a small panel must be kept below about 10-9 g/day and 10-8 cm3/atm/day, respectively. In order to achieve these levels, not only the bulk permeability but also the control of the adhesion of the sealant to the glass seems to be an important factor of the sealing material. So, desiccants are essential to improve the tolerance for this influx, as well as to soak up water or oxygen that desorb from the materials inside the device after sealing. Feasibility of such a resin and getter for OLEDs encapsulation has been evaluated by analysis of physical and electrical properties of resins and getters. In particular, driving voltage/luminance/lifetime of simple OLEDs (glass / ITO / PEDOT:PSS / NPD / Alq3 / LiF / Al) have been measured. Devices have been encapsulated immediately after fabrication, using a resin as sealant and different getters from SAES as desiccants. Devices have aged for 200 hours in different accelerated lifetime conditions. The beneficial effect of the getter is discussed.

Authors, based on years of experience in the field of printed electronics, present in the paper the last achievements in the producing of high quality thick-film printed composite resistors. For the testing purposes the following paste compositions were prepared: as a binder a polystyrene and styrene-butadiene-styrene compounds were applied and as a fillers carbon black, graphite and CNT (carbon nanotubes) were added to the compositions. The pastes were deposited on flexible polymer substrates and cured in the temperature range 120 ÷ 200ºC. The electrical (R, TCR, δR) and mechanical properties of every group of resistors were tested in wide range of temperature (- 30 ÷ + 80 ºC). The results are presented on many charts and in tables showing the behavior of resistors under the influence of various conditions, as well as long period stability. Also the mechanism of conduction for different resistive compositions was considered and authors applied for this purpose the Holm’s theory of electrical contacts. Assuming the properties of composition resistors the authors propose the fields of applications i.a. such as: parts of electronic circuits, temperature and stress sensors, heaters. Literature: 1. Sandler J.K.W., Kirk J.E., Kinloch I.A., Shaffer M.S.P., Windle A.H., „Ultra-low electrical percolation threshold in carbon nanotubes-epoxy composites”, Polymer 44 (2003), pp.5893 – 5899 2. Holm. R., “Electric Contacts”, Springer Verlag, Berlin, Heidelberg, New York 1979 3. Łukasik A., “Degradation in carbon-polyester fim pressure sensors”, XXXI International Conference of IMAPS Poland Chapter, Rzeszów – Krasiczyn, 23-26 September 2007. pp.359 – 362 4. Jakubowska M., Łukasik A., Młożniak A., Słoma M., „Resistive pressure sensors fabricated from polimer trick-film composites containing carbon nanotubes”, Materiały Elektroniczne 36 (2008), nr 3, pp. 92 - 99

Thick film technology is very advantageous because of ease of processing, reliability and low cost. We have developed pyroelectric and piezoelectric sensors directly deposed on paper substrate by screen printing. The devices have been fabricated with new polymer inks based on Lead zirconate titanate (PZT). Lead zirconate titanate (PZT) are widely used as sensors, actuators, and transducers due to their excellent piezoelectric performances, but few devices using PZT thick film[1,2]. PZT presents pyroelectric and piezoelectric properties. The characteristics of these devices depend how the PZT thick film is poled. A description of the manufacturing process of PZT thick film devices will be given and the dependency of their pyroelectric and piezoelectric properties from their polarization will be described. The sensors are constituted of 5 layers, one layer for each electrode and 3 PZT layers, for a total thickness of approximately 50μm. A polarization is necessary because of the random alignment of the ferroelectric domains of the PZT. The poling process consists to place the substrate on a hotplate and to heat the device until 200°C [3]. In the same time, a poling field is applied through the electrode. The poling parameters; heating temperature, magnitude of the poling field, are chosen depending on the physical properties of PZT layer; its thickness, its quality and its dielectric properties. The last step is the measurement of the pyroelectric and piezoelectric properties of the poled PZT layer. The pyroelectric properties are determined by applying variations of temperature to the device and simultaneously by measuring the current generated. So a typical pyroelectric coefficient is deduced homogeneous to C.K-1.m-2 (about 30 μC.K-1.m-2). The piezoelectric d33 coefficient (C.N-1) is also measured by applying a stress to the layer (about 15 pC.N-1). More these two coefficients are important more the poling process is optimized.

In the automotive industry, the combination of an electrochromic shading function and a polycarbonate window displays an attractive alternative to the current panorama glass roof. It enables the improvement of comfort and space feeling of customers while reducing the weight of vehicles and avoiding overheating of the interior and blending effects. Using polymer windows also offers easier processing and higher design freedom. The electrochromic function enables to switch the transparency of the window from dark to bright by applying a small electrical voltage. This technology is already available on the market for some applications like rear-view mirrors, however using glass as substrate. Due to the long life cycle of vehicles, the ageing of a polycarbonate based electrochromic device and its components must be investigated in detail before any application in this domain. In this study, the influence of a high humidity (75%rH) exposure and the mechanical ageing caused by bending were investigated for components of the electrochromic assembly. An electrochromic conductive polymer PEDT/PSS layer and two types of titanium oxide as ion storage layer were tested. The commercially available formulation of PEDT/PSS and titanium oxides were coated onto an ITO layer sputtered polycarbonate substrate. The influence of humidity exposure and mechanical ageing were characterized using UV-VIS-NIR spectrometry (300-2600nm) and sheet resistance measurements. Measurements were carried out during humidity exposure, as well as before and after the mechanical stress. As a result, the main part of degradation is caused by humidity exposure inducing a loss of conductivity. The mechanical ageing turns out to have a very minor impact on the optical and electrical properties of the layers.

Nowadays radio frequency identification (RFID) tags are widely demanded in many applications that require automatic control of massive objects. To save the considerable cost of IC chips in the conventional tags, a chipless RFID tag where ID information is encoded using multiple inductor-capacitor (LC) resonant circuits was previously presented. Although the authors pointed out that printability of the planar LC configuration could make the manufacturing cost of the tags much lower, unfortunately the ultralow-cost printed tags were not fully realized and investigated. In this work we fabricate the RFID tags using inkjet printing technology and evaluate their performances both theoretically and experimentally. These tags are built up in a sandwich structure. The conductors of the inductors and one of the parallel plate electrodes of the capacitors are printed on one substrate, while the other electrode is printed separately on another substrate. These two substrates are then stacked together with a dielectric layer sandwiched between the capacitor-electrodes. Separation of the printing substrate and the dielectric layer makes the design and manufacture of the tags more flexible, and also eliminates the requirement of via. The sandwich structure makes the tag suitable for roll-to-roll manufacture, ensure high-volume production, and therefore make the RFID tag ultralow-cost. Design flow and two detection methods: single-loop antenna and two-loop antenna setups, will be introduced and discussed. Due to lower conductivity and lower thickness of inkjet-printed nanoparticle metal as compared with its bulk counterpart, several performance parameters which are related to the quality factor of LC circuits are inevitably degraded, such as reading distance, signal to noise ratio. Thus the limitation of the inkjet-printed RFID tags in application will also be discussed.

The search for the W-OLED (White-Organic Light Emitting Diode) is one of the most important areas for new efficient lighting, both for general and for decorative applications. One of the most usual ways to achieve the white or near-white emission is the multi-photon device where different and independent layers emit in the RGB system. Such structure is sometimes complex and with poor reproducibility. Another way is use the two organic emitters in complementary colors imbibed together in the active layer. In the present work, a low-cost W-OLED (white - organic light emitting diode) was developed specifically aimed at applications for decorative lighting. The general concept was to use two organic emitters with complementary colors, NPB and DCM1. The approach to white emission is tuned by changing the DCM1 percentage in the NPB host matrix, ranging from 1 to 2%. The basic OLED structure was NPB:dye/BCP/Alq3. All layers are thermally evaporated. Best results are obtained for DCM1 percentages of 1% with (x, y) color coordinates of (0.30, 0.32). The typical radiometric power ranges from 200 to 500 mW (full emission bands) with wall-plug efficiency over 2%. When the dye is changed to Rubrene, in the same OLED structure, the best result are yellowish-white emission with typical coordinates near (0.42, 0.40), but with higher radiometric power emission (over 300 mW minimum) although similar wall-plug efficiencies. The easiness of obtaining a more wide color emission (from more reddish to greenish-white, when the Rubrene percentage changes from 4 to 1%) makes such blend more suitable for decorative applications. All electroluminescence spectra exhibit only the NPB and dye emission bands. With such data, small-scale prototypes for commercial decorative lighting applications are being presented. Currently, decorative lighting systems based on a small-scale array of OLEDs for pattern lighting are being integrated onto conventional indoor structures.

HIFLEX is an EU FP7 ICT project (Start 1st of January 2010, End December 2012) with the aim to develop a cost-effective Highly Flexible Printed ITO-free Organic Photovoltaics (OPV) module technology that matches the particular requirements of mobile and remote ICT applications, delivering the required efficiency under different light conditions, sufficient lifetime, acceptable cost structure, appropriate power-to-weight ratio and fit-to-purpose mechanical flexibility. The work that has been performed since the beginning of this project can be summarized as follows: • Design, fabrication and first performance evaluation of ITO benchmark and ITO-free device structures • Development of low resistance ITO-free substrates composed of current collecting printed grids and highly conductive PEDOTs • Development of fabrication technologies for optimal S2S and R2R processing of OPV • Electrical modelling to design optimal cell and module structures for ITO-free device concepts and experimental validation • First evaluation of large Area characterization methods (optical inspection, LBIC) for process control • R2R production of ITO-based and ITO-free module structures • Life Cycle Analysis In this contribution, a selection of highlights will be presented with specific attention to a systematic study which was carried out recently to investigate the effect of grid line density (pitch size), grid finger length and height on the performance of a large series ITO free OPV single cells ranging in size from 1 to 15 cm2. The composite front electrode consisted of current collecting grid silver lines prepared by ink jet printing or evaporation and a semitransparent PEDOT:PSS conductor. The measurements are supported by a careful modeling study enabling rational designs of optimal grid structures for ITO free cells and modules for different types of applications. An imaging technique like LBIC has shown to be very useful tool to map the current distribution over the device area and to visualize defects, degradation effects in these type of cells. *The abstract is written on behalf of all the consortium members

OLEDs with a two-dimensional photonic crystal (PC) structure have been fabricated by several groups and actually this approach is one of the best answers to improve their efficiency. Many researchers have been working for years on this issue finding an enhancement of 50% and 140% in the luminance efficiency and the peak intensity, respectively. On the other hand the use of this technique causes a change not only in the far field but also in the emission spectrum depending on the used geometry, which must be taken into account in applications that must be used in an established framework. In particular, this drawback becomes prominent in applications involving the use of a flexible substrate, and may be quite irritating in many applications, even thought it may be crucial for the improvement of sensor applications in the organic electronics platform. The use of OLED and PC on flexible substrate, in fact, can give the opportunity to realize a sensible device because of the bending effect on the PC structure. To this purpose, a 2D-PC pattern with different lattice constants has been realized by Electron Beam Lithography technique (EBL) on a surface of 2x2 mm2 removing partially a resist co-polymer (ZEP-520) deposited on a thin Indium Tin Oxide (ITO) grown itself on a PET substrate. An optical setup was adopted to measure the light propagating in the PET substrate which is extracted by diffraction and to evaluate the change in the PC properties and consequently on the emitted spectra changing the bend strain. Finally we realized an OLED device on the other side of the substrate to test the possibility to realize a new class of sensible device because of the change in the radius of curvature of the substrate and then the response of the photonic structure.

Organic electronic devices are very attractive for next generation display. But, it can be easily degraded by reaction with moisture or oxygen molecules in the ambient condition. In order to prevent these kinds of degradation from molecules in the air, rigid cover glasses are usually used in encapsulation process for organic electronics. Encapsulation process has become a necessarily required process in recent organic devices for enhancing device durability. However, conventional encapsulation using a rigid cover glass and large amount of desiccants has critical drawbacks such as non-flexibility, need of desiccant, and incompatibility with roll-to-roll processing. We report novel encapsulation method(Flex Lami-capsulation) using thin metal foils coated with a polymer. Devices with the Flex Lami-capsulation exhibit similar durability compared with that of glass encapsulation. The Flex Lami-capsulation can be a useful method to passivate flexible displays or organic devices during roll-to-roll process.

In this work, a novel method for electrode modification based on inkjet-printing of electrochemically synthesized graphene-PEDOT:PSS (GP-PEDOT:PSS) nanocomposite is reported for the first time. GP-PEDOT:PSS dispersed solution is prepared for use as an ink by one-step electrolytic exfoliation from a graphite electrode. GP-PEDOT:PSS layers are then printed on screen printed carbon electrodes (SPCEs) by a commercial inkjet material printer (Dimatrix Inc.) and their electrochemical behaviors are characterized towards three most common electroactive analytes including hydrogen peroxide (H2O2), nicotinamide adenine dinucleotide (NAD+/NADH) and ferri/ferro cyanide (Fe(CN)63-/4-) redox couples. It is found that the oxidation signals for H2O2 , NADH and K2Fe(CN)6 of PEDOT:PSS modified and GP-PEDOT:PSS modified SPCEs are ~2-4 and ~3-13 times higher than those of unmodified SPCE, respectively. In addition, excellent analytical features with relatively wide dynamic ranges, high sensitivities and low detection limits have been achieved. Therefore, the inkjet-printed GP-PEDOT:PSS electrode is a promising candidate for advanced electrochemical sensing applications.

Systems-in-Foil concept addresses the integration of electronic components onto flexible polymeric substrates. Nowadays, the integration of components such as silicon chips and discrete elements is being investigated. However, the fully integration and interconnection of printed components on flexible polymers (e.g. printed sensors) to different polymeric substrates (e.g. smart labels) has not yet been fully covered. This integration will enhance the functionality and versatility of polymeric smart systems, as well as reduce the development feed-back loop of components. Mechanically robustness and large-area processing are key factors to achieve low-cost and high-throughput polymeric device fabrication. Additionally, low-temperature processing is required due to temperature restrictions related to the relatively low glass transition temperature of some polymers. For these reasons, we report on a low-temperature mechanical and electrical integration of a sensor printed on PET foil onto a polymeric label containing printed metal tracks. Two different techniques are presented and compared, highlighting their benefits regarding high-throughput feasibility. The first approach uses anisotropic conductive adhesives (ACA’s), which is stencil printed and cured at relatively low temperatures. This approach takes advantage of the ACA’s unidirectional conductivity (across its thickness) and its adhesion properties to polymers. The second approach uses pressure sensitive adhesives (PSA’s) for the mechanical assembling and vias through its thickness to electrically interconnect the foils. First, laser-ablated vias through the PSA are filled with screen printed silver ink. Finally, after sensor foil alignment, the conductive ink within the vias is cured at relatively low temperatures. The use of the reported processes can be extended to integrate other electronic components, silicon or foil based. Cyclic bending tests are on-going in order to assess the mechanical robustness of the fabricated devices. First preliminary results are very promising showing no delamination failures, one of the most important issues regarding foil-to-foil integration reliability.

Flexible, organic and large area electronics are growing in interest and complexity. In the last few years some authors have been focusing on the importance of printing somewhat processing structures in order to embed digital control over basic organic sensors and actuators thus making organics a real and complete electronic systems technology. On the other hand, we have organic chemistry which is still far from offering inks and materials fulfilling the requirements of usual electronic systems (mainly in terms of both reliability and performance). As a result, designers of organic electronic systems are more engaged to materials limitations than ever inorganic silicon-based designers were in the past. This tedious work has made organic developers to let aside well known microelectronic basic rules, for system design, which come from the experience of decades on inorganic design, specifically for the digital domain what is the case of our contribution. In this work, we review the essence of digital design in order to offer criteria to the OLAE community to build more efficient electronic systems. The main idea is that efficiency is linked to the number of transistors. By reducing them one can increase reliability without losing speed performance. The easiest way to reduce the number of transistors, in a digital system, is by the use of a carefully designed cell-library as it has been done in almost all inorganic silicon processes. This paper shows, by just using very simple cells, how in nowadays examples of organic electronics systems (i.e. 8-bit microprocessor from IMEC) the number of transistors could be reduced around 15% and up to 40% in case of using a bit more complex structures keeping functionality and processing speed. If we also use the inorganic electronics concept of transistors density (transistors per square millimeter) we can also say that important reductions in area will take place, leaving more space to other system components (like sensors, displays, batteries, etc).

Radio frequency identification (RFID) is a technology which uses RF signals for automatic identification. The application area for RFID is now huge – from retail item management to electronic toll collection. Printed electronics technologies have brought the possibility to produce RFID tags and especially antennas significantly more lower costs than with traditional techniques. Printed RFID tags typically use silver for antennas which is subject to price hikes. This means that raw materials require more optimised usage which can be assessed through modelling. In this study we used inkjet printed RFID antennas for UHF range. The point of the study was to find the correlation between inkjetted layer thicknesses and RFID reading distance and how the layer thickness affects to the RFID antennas other properties as peak response frequency. An electromagnetic simulator was used for antenna simulations and from the simulation results the reading distance was processed with engineering calculation software. In the first simulation the antenna thickness was varied from 1 to 10 µm and the material used was copper. As results the antenna reading distance changes from 8.66 to 8.69 meters at peak frequency 964 MHz. For the final version more simulations will be done by using printed silver conductors which conductivity is lower. The antenna simulation results also correlated with the measurement results of the inkjet printed RFID tags. The study of the RFID antenna layer thickness effects on antenna performance allows the optimisation of inkjet printing process. The simulations also suggest that further optimisation can be done by varying the antenna thickness for example by increasing thickness in areas where current density is high. This allows the most optimal use of conductive ink which affects to the production costs.

Printed organic thin film transistors (OTFT) start to be widely used for flexible and low cost electronic circuits. In order to produce reliable systems and to make this technology widely accessible to circuit designers, simple but precise models for simulations have to be applied. The simple Shichman-Hodges Model [1] - with extensions of the subthreshold - and saturation behaviour and the variable Range Hopping (VRH) Model [2] are compared with measurements of printed OTFTs and the differences will be explained in detail. Therefore transfer and output characteristics are compared. The measurements for comparison and parameter extraction have been performed according to the electrical procedures as described in [3,4] to ensure reproducibility and on the substrate described herein. The VRH model has been implemented in a commercial circuit development system. Examples of circuit simulations will be shown. Furthermore the results of a layout generator available on the system are presented. This work has been supported by the German Federal Ministry of Education and Research (BMBF) within the project Polytos OSS1 within the cluster of excellence Forum Organic Electronics (project no. 13N10204 – 14).

Inkjet printing is a challenging technique that will lead to a new paradigm in electronics fabrication through the construction of electronic devices and circuits drop by drop. However, inkjet technology for Printed Electronics is still under development and several challenges remain. While there is significant progress in the development of electronic devices, such as organic transistors, there is a lack of work on circuit and system level design. Designing devices and circuits requires a wide knowledge of process aspects and a complex interaction among concepts, tools and processes coming from different science and engineering disciplines. Our proposal is based on the experience of the silicon foundry model, and the idea of the process design kit (PDK) as the nexus between design and technology. PDK basic information contents are given in terms of geometrical and electrical design rules, device technology parameters and simulation models. A methodology to extract and characterize inkjet geometric Design Rules is proposed in this work as a first step to separate design from fabrication in a similar way as in silicon technology design, to develop devices and systems without a deep knowledge of process and materials. Geometric design rules aim to guarantee that layout representations match final printed patterns within a valid tolerance for a desired process yield. The more conservative the rules are, the better is the yield. Although they can comprise a very large set of restrictions, they are based on two considerations: (1) the geometrical patterns that can be reproduced by the process and (2) the interaction between different layers. So, for a given process and after an experimental extraction of the required process parameters, it is possible to derive minimum design rules that characterize the technology process to a point where design engineers can address physical design with sufficient certainty.

A method to extract crucial material and device parameters of organic bulk hetero-junction solar cells from experimental data is presented. Accurate device characterization is an essential part in research and development of solar cells. Obtaining reliable material and device parameters is an important step in this characterization, since it paves the way to a better understanding of device operation and the quantification of loss mechanisms. Parameter extraction is an error-prone task and the obtained values often lack accuracy. Using inaccurate material or device parameters can lead to misleading interpretation of results. We present a method to extract material and device parameters more accurately. To reduce the correlation among the extracted parameters we simultaneously analyze the current-voltage characteristics, the transient photo-CELIV current and the dynamic response to a light pulse. We show that with numerical modeling based on one set of parameters a systematic series of measurements can be reproduced. The full electrical behavior can be described using a basic drift-diffusion model with constant mobilities and direct photon-to-charge conversion.