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Long‐chain organic halide salts are widely used in perovskite‐based optoelectronic devices for surface passivation owing to their capability to interact with the surface defects of perovskites. Here, aluminum oxide (AlOx) is introduced via atomic layer deposition onto octylammonium iodide (OAI) to exploit the benefits of organic halide salts without generating undesired defects. The devices incorporating AlOx on OAI‐treated perovskite (OAI/AlOx) show enhancement in both device performance and photo‐stability compared to those with only treatment. A diffusion of aluminum from AlOx into the perovskite through surface characterization contributes to a uniform photo‐generated carrier transport in both the surface and the bulk of the perovskite absorber. In addition, it is revealed that light‐induced two‐dimensional perovskite formation on OAI/AlOx. This may be ascribed to preventing the loss of OA cations due to the presence of AlOx, leading to a decrease in the number of iodine anions which suppresses the light‐induced degradation of corresponding devices. Consequently, the devices show over 24% efficiency and retain their efficiency over 1000 hours under continuous light illumination. [ABSTRACT FROM AUTHOR]

Ternary zinc tin oxide (ZTO) is one of the few environmental compatible buffer materials with the potential of replacing the n-CdS buffer in Cu(In,Ga)Se2 (CIGS) solar cells and other photovoltaic systems once its properties are fully understood and optimized. In this work, ZTO films were grown by atomic layer deposition and were logically characterized with the aim of understanding the correlations between compositional changes and film properties. The ZnO:SnO2 pulse ratio significantly affected the growth rate, crystal structure, morphology, and band gap of the ZTO films. By controlling the Sn/(Sn + Zn) atomic ratio, the optical band gap of the ZTO films was tuned between 3.05 and 3.36 eV. Integrating the ZTO films as buffer layers in CIGS solar cells, we observed that films with Sn concentrations of 9 to 16 at.% yielded photo-conversion efficiency close to 14%, which was very comparable to efficiency attained with the commonly used CdS buffer. Furthermore, using X-ray photoelectron spectroscopy analysis, we correlated the current-voltage behavior of the cells to the conduction band offset at the ZTO/CIGS interface. [ABSTRACT FROM AUTHOR]