MoO3 films spin‐coated from a suspension of nanoparticles, which offers energetic properties nearly identical to those of thermally evaporated MoO3 films, are reported. It is demonstrated that our solution‐based MoO3 acts as a very efficient hole‐injection layer for organic devices.

Highly efficient gas‐diffusion barriers based on nanolaminates of alternating Al2O3 and ZrO2 layers grown at 80 °C by atomic‐layer deposition are presented. Ultralow water‐vapor permeation rates are reported, and a dramatic reduction of statistical defects on larger areas was found compared to single Al2O3 layers. This study provides a concept for the encapsulation of organic optoelectronic devices.

A common phenomenon of organic solar cells (OSCs) incorporating metal‐oxide electron extraction layers is the requirement to expose the devices to UV light in order to improve device characteristics – known as the so‐called “light‐soaking” issue. This behaviour appears to be of general validity for various metal‐oxide layers, various organic donor/acceptor systems, and regardless if single junction devices or multi stacked cells are considered. The requirement of UV exposure of OSCs may impose severe problems if substrates with limited UV transmission, UV blocking filters or UV to VIS down‐conversion concepts are applied. In this paper, we will demonstrate that this issue can be overcome by the use of Al doped ZnO (AZO) as electron extraction interlayer. In contrast to devices based on TiOx and ZnO, the AZO devices show well‐behaved solar cell characteristics with a high fill factor (FF) and power conversion efficiency (PCE) even without the UV spectral components of the AM1.5 solar spectrum. As opposed to previous claims, our results indicate that the origin of s‐shaped characteristics of the OSCs is the metal‐oxide/organic interface. The electronic structures of the TiOx/fullerene and AZO/fullerene interfaces are studied by photoelectron spectroscopy, revealing an electron extraction barrier for the TiOx/fullerene case and facilitated electron extraction for AZO/fullerene. These results are of general relevance for organic solar cells based on various donor acceptor active systems.

Metal-halide perovskite semiconductors are of tremendous interest for a variety of applications. Only recently, solar cells based on a representative of this family have been certified with an efficiency in excess of 24%.[1] Aside from their remarkable success in photovoltaics, metal-halide perovskites are also highly promising as light emitters, e.g., in light-emitting diodes (LEDs) or lasers. [2][3][4] LEDs based on the fruit-fly of these compounds, i.e., methylammonium lead iodide (CH 3 NH 3 PbI 3 or MAPbI 3 ), and other related perovskites have been demonstrated with continuously increasing efficiency. [5][6][7] For lasers, there is the vision that perovskites may overcome/avoid the typical limitations and loss mechanisms present in organic gain media, such as triplet-singlet annihilation or absorption due to triplet excitons and Cesium lead halide perovskites are of interest for light-emitting diodes and lasers. So far, thin-films of CsPbX 3 have typically afforded very low photoluminescence quantum yields (PL-QY < 20%) and amplified spontaneous emission (ASE) only at cryogenic temperatures, as defect related nonradiative recombination dominated at room temperature (RT). There is a current belief that, for efficient light emission from lead halide perovskites at RT, the charge carriers/excitons need to be confined on the nanometer scale, like in CsPbX 3 nanoparticles (NPs).Here, thin films of cesium lead bromide, which show a high PL-QY of 68% and low-threshold ASE at RT, are presented. As-deposited layers are recrystallized by thermal imprint, which results in continuous films (100% coverage of the substrate), composed of large crystals with micrometer lateral extension. Using these layers, the first cesium lead bromide thin-film distributed feedback and vertical cavity surface emitting lasers with ultralow threshold at RT that do not rely on the use of NPs are demonstrated. It is foreseen that these results will have a broader impact beyond perovskite lasers and will advise a revision of the paradigm that efficient light emission from CsPbX 3 perovskites can only be achieved with NPs.

Entirely transparent pixels composed of monolithically integrated transparent organic light‐emitting diodes driven by transparent thin‐film transistors are presented. With an average transmittance of more than 70 % (see figure and inside cover) in the visible part of the spectrum (400–750 nm), the presented active pixels pave the way to the realization of fully transparent active‐matrix displays. Low processing temperatures mean that flexible transparent displays may be feasible.