All-inkjet printed large area organic solar cells deposited from environmentally friendly solvents are demonstrated for the first time.

Flexible semi‐transparent organic photovoltaic (OPV) modules were manufactured by roll‐to‐roll slot–die coating of three functional layers [ZnO, photoactive layer, and poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)] and either the screen printing or inkjet printing of the top electrodes. A poly(3‐hexylthiophene):[6,6] phenyl C61‐butyric acid methyl ester (P3HT:PCBM) layer deposited from non‐chlorinated solvents was used as the absorber layer. The modules were realized by slot–die coating of the layers onto a laser‐patterned polyethylene terephthalate/indium‐tin oxide (PET/ITO) substrate, followed by laser structuring of all coated layers. The top electrodes were realized by high‐resolution printing, which, combined with laser patterning of other layers, enables manufacturing of the modules with high geometrical fill factor (92.5 %). The modules have an active area of 156 cm2, and contain 13 serially interconnected cells. Two semitransparent electrodes (ITO from the bottom and PEDOT:PSS/Ag‐grid from the top side) allow the absorption of photons incident from both sides. The performance of the modules was evaluated and compared among the modules by considering the following factors: (i) roll‐to‐roll slot–die coated vs. spin‐coated layers, (ii) inkjet‐printed vs. screen‐printed top electrodes, (iii) top vs. bottom illumination. The demonstrated technology is one of the proven feasible ways towards industrial manufacturing of the OPV modules.

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Electro-optical devices are key in current information and communication technology. Whereas the familiar cathode ray tube can be considered to be a mature technology, other device principles, such as plasma-addressed devices, [1] and field-emission, [2] electroluminescent, [3,4] electrochromic, [5] and electrophoretic displays, [6] are still at various stages of development, implementation, and market acceptance. Flat and light-weight liquid-crystal-based devices are currently considered to be the main alternative to the cathode ray tube, and various switching principles have been developed, such as p-cells, [7] twisted [8] and super-twisted nematic, [9] ferroelectric, [10] and vertically aligned nematic [11] liquid-crystal displays. Devices based on these different principles all have their own specific advantages with respect to characteristics such as switching kinetics, switching voltages, energy consumption, and viewing angle dependency. In order for these devices to function optimally, microscopic control over the director of the liquid-crystal molecules within the device is required. This is enforced by the boundary conditions of the liquid-crystal layer, and is preferably realized through alignment layers. Whereas conventional uniaxial alignment is sufficient for less demanding applications, more sophisticated, patterned alignment is needed to improve the optical performance of devices further, for instance with respect to the viewing angle. One application of patterned alignment is in multidomain displays that exhibit reduced viewing angle dependence and reduced gray-scale inversion. [12,13] Several methods can be used to align liquid crystals. Traditionally, surfactants or mechanical rubbing methods of polyimides are employed. [14] However, this procedure requires direct mechanical contact, which introduces defects and is a source of electrostatic discharge and dust. The patterned alignment in different directions on a single substrate requires the additional use of photoresists, which is both laborious and cumbersome. Photo-alignment using (linearly polarized) light in combination with a photomask offers a non-contact alternative that enables bi-directional control over the alignment.[15±17] However, accurate and reproducible control over the pretilt angle of the liquid crystals is complicated, and the technique suffers from adverse side effects such as image sticking. It is also extremely difficult to realize control over both the azimuthal and polar anchoring of the liquid crystals within a single substrate. Combinations of both unidirectional planar (in the plane of the substrate) and homeotropic (perpendicular to the plane of the substrate) alignment of liquid crystals within a single substrate has been realized using micro-contact printing of self-assembled monolayers on relatively thick, semi-transparent gold layers, [18] and on transparent ultra-thin gold layers. [19] Other reported alignment methods, such as the use of expensive atomic beams, also only provide bi-directional control of the azi...