The combination of inorganic semiconductors with organic thin films promises new strategies for the realization of complex hybrid optoelectronic devices. Oxidative chemical vapor deposition (oCVD) of conductive polymers offers a flexible and scalable path towards high-quality three-dimensional inorganic/organic optoelectronic structures. Here, hole-conductive poly(3,4-ethylenedioxythiophene) (PEDOT) grown by oxidative chemical vapor deposition is used to fabricate transparent and conformal wrap-around p-type contacts on three-dimensional microLEDs with large aspect ratios, a yet unsolved challenge in three-dimensional gallium nitride technology. The electrical characteristics of two-dimensional reference structures confirm the quasi-metallic state of the polymer, show high rectification ratios, and exhibit excellent thermal and temporal stability. We analyze the electroluminescence from a three-dimensional hybrid microrod/polymer LED array and demonstrate its improved optical properties compared with a purely inorganic microrod LED. The findings highlight a way towards the fabrication of hybrid three-dimensional optoelectronics on the sub-micron scale.

Solar cells based on hybrid organic/inorganic perovskites have shown an astonishing efficiency development in the past years, having peaked in power conversion efficiencies of >25% for small‐area single‐junction devices. To pave the way for future commercialization, however, high power conversion efficiencies also have to be demonstrated on areas multiple orders of magnitude larger. Herein, methylammonium‐free perovskite photovoltaic modules with an active area of 66 cm2 are presented. All functional layers processable from solution are deposited by blade coating without the use of an antisolvent, demonstrating the feasibility of this approach for large‐area module fabrication. The coating process is analyzed in detail and a model based on the Landau–Levich problem is developed for the blade‐coating setup. The perovskite crystallinity can be improved by the addition of lead(II) thiocyanate, which results in increased crystallite size as judged by Williamson–Hall's analysis of X‐ray diffraction data and corresponding scanning electron microscopy images. The homogeneity of the final modules is investigated with dark lock‐in thermography and electroluminescence imaging, indicating only few shunts in the module area. Modules are made up of 15 serially interconnected solar cells and reveal a stabilized efficiency of 12.6% under maximum power point tracking.

GaN fins on GaN-on-sapphire templates are fabricated by continuous mode selective area metalorganic vapor phase epitaxy. The fins exhibit high aspect ratios and smooth nonpolar aplane sidewalls with an ultra-low threading dislocation density of a few 10 5 cm -2 making them ideally suited for optoelectronic to electronic applications. A detailed analysis of the inner structure of GaN fins is provided by the help of marker layer experiments and correlation of results from fins fabricated under different growth conditions, leading to the development of a growth model to explain the final geometry and optical as well as electrical properties of these high aspect ratio fins. Distinctly different material properties for the central and outer parts of the fins are detected. Whereas the outer sidewalls represent high quality GaN surfaces with

Three-dimensional InGaN/GaN nano-and microstructures with high aspect ratios and large active sidewall areas are still of great interest in the field of optoelectronics. However, when grown by metalorganic chemical vapor deposition (MOCVD), their optical performance can be negatively affected by gradients in thickness and peak emission wavelength along their sidewalls, which is still a key obstacle for using such structures in commercial products. In this work, we present a detailed study on the different mechanisms causing this gradient, as well as means to alleviate it. Gas-phase mass transport and surface diffusion are found to be the two main processes governing the shell growth, and the predominance of one process over the other is varying with the geometry of the 3D structures as well as the spacing between them. Consequently, variations in temperature, which mainly affect surface diffusion, will have a stronger impact on structures with small separation between them rather than larger ones. On the other hand, variations in pressure modify gas-phase diffusion, and thus, structures with a large spacing will be more strongly affected. A proper design of the dimensions of 3D architectures as well as the separation between them may improve the gradient along the sidewalls, but a tradeoff with the active area per wafer footprint is inevitable.

The commonly observed absorption around 265 nm in AlN is hampering the outcoupling efficiency of light‐emitting diodes (LEDs) emitting in the UV‐C regime. Carbon impurities in the nitrogen sublattice (CN) of AlN are believed to be the origin of this absorption. A specially tailored experiment using a combination of ion implantation of boron, carbon, and neon with subsequent high‐temperature annealing allows to separate the influence of intrinsic point defects and carbon impurities regarding this absorption. Herein, the presented results reveal the relevance of the intrinsic nitrogen‐vacancy defect VN. This is in contradiction to the established explanation based on CN defects as the defect causing the 265 nm absorption and will be crucial for further UV‐LED improvement. Finally, in this article, a new interpretation of the 265 nm absorption is introduced, which is corroborated by density functional theory (DFT) results from the past decade, which are reviewed and discussed based on the new findings.