A hybrid approach for the realization of In-free transparent conductive layers based on a composite of a mesh of silver nanowires (NWs) and a conductive metal-oxide is demonstrated. As metal-oxide room-temperature-processed sol–gel SnO_x or Al:ZnO prepared by low-temperature (100 °C) atomic layer deposition is used, respectively. In this concept, the metal-oxide is intended to fuse the wires together and also to “glue” them to the substrate. As a result, a low sheet resistance down to 5.2 Ω sq^-1 is achieved with a concomitant average transmission of 87%. The adhesion of the NWs to the substrate is significantly improved and the resulting composites withstand adhesion tests without loss in conductivity. Owing to the low processing temperatures, this concept allows highly robust, highly conductive, and transparent coatings even on top of temperature sensitive objects, for example, polymer foils, organic devices. These Indium- and PEDOT:PSS-free hybrid layers are successfully implemented as transparent top-electrodes in efficient all-solution-processed semitransparent organic solar cells. It is obvious that this approach is not limited to organic solar cells but will generally be applicable in devices which require transparent electrodes.

Atmospheric-pressure plasma atomic layer deposition (APP-ALD) of TiO_x at room temperature is reported for the first time. Layer properties of the APP-ALD-grown TiO_x are compared to those reported for the low-pressure plasma ALD of TiO_x. The contribution of parasitic CVD to the process is discussed. The application of the resulting TiO_x layers as electron-extraction interlayers in inverted organic solar cells (OSCs) is demonstrated. The characteristics of OSCs based on APP-ALD-grown TiO_x are similar to those of OSCs based on TiO_x prepared by low-pressure thermal ALD or sol-gel processing. APP-ALD is intended to harvest the beneficial properties of ALD layers in a high-throughput atmospheric processing environment.

For large-scale and high-throughput production of organic solar cells (OSCs), liquid processing of the functional layers is desired. We demonstrate inverted bulk-heterojunction organic solar cells (OSCs) with a sol–gel derived V₂O₅ hole-extraction-layer on top of the active organic layer. The V₂O₅ layers are prepared in ambient air using Vanadium(V)-oxitriisopropoxide as precursor. Without any post-annealing or plasma treatment, a high work function of the V₂O₅ layers is confirmed by both Kelvin probe analysis and ultraviolet photoelectron spectroscopy (UPS). Using UPS and inverse photoelectron spectroscopy (IPES), we show that the electronic structure of the solution processed V₂O₅ layers is similar to that of thermally evaporated V₂O₅ layers which have been exposed to ambient air. Optimization of the sol gel process leads to inverted OSCs with solution based V₂O₅ layers that show power conversion efficiencies similar to that of control devices with V₂O₅ layers prepared in high-vacuum.

The mechanism of charge generation in transition metal oxide (TMO)-based charge-generation layers (CGL) used in stacked organic light-emitting diodes (OLEDs) is reported upon. An interconnecting unit between two vertically stacked OLEDs, consisting of an abrupt heterointerface between a Cs₂CO₃-doped 4,7-diphenyl-1,10-phenanthroline layer and a WO₃ film is investigated. Minimum thicknesses are determined for these layers to allow for simultaneous operation of both sub-OLEDs in the stacked device. Luminance–current density–voltage measurements, angular dependent spectral emission characteristics, and optical device simulations lead to minimum thicknesses of the n-type doped layer and the TMO layer of 5 and 2.5 nm, respectively. Using data on interface energetic determined by ultraviolet photoelectron and inverse photoemission spectroscopy, it is shown that the actual charge generation occurs between the WO₃ layer and its neighboring hole-transport material, 4,4',4”-tris(N-carbazolyl)-triphenyl amine. The role of the adjacent n-type doped electron transport layer is only to facilitate electron injection from the TMO into the adjacent sub-OLED.