The chemical composition engineering of lead halide perovskites via a partial or complete replacement of toxic Pb with tin has been widely reported as a feasible process due to the suitable ionic radius of Sn and its possibility of existing in the +2 state. Interestingly, a complete replacement narrows the bandgap while a partial replacement gives an anomalous phenomenon involving a further narrowing of bandgap relative to the pure Pb and Sn halide perovskite compounds. Unfortunately, the merits of this anomalous behavior have not been properly harnessed. Although promising progress has been made to advance the properties and performance of Sn‐based perovskite systems, their photovoltaic (PV) parameters are still significantly inferior to those of the Pb‐based analogs. This review summarizes the current progress and challenges in the preparation, morphological and photophysical properties of Sn‐based halide perovskites, and how these affect their PV performance. Although it can be argued that the Pb halide perovskite systems may remain the most sought after technology in the field of thin film perovskite PV, prospective research directions are suggested to advance the properties of Sn halide perovskite materials for improved device performance.

Interface strains and lattice distortion are inevitable issues during perovskite crystallization. Silane as a coupling agent is a popular connector to enhance the compatibility between inorganic and organic materials in semiconductor devices. Herein, a protonated amine silane coupling agent (PASCA‐Br) interlayer between TiO2 and perovskite layers is adopted to directionally grasp both of them by forming the structural component of a lattice unit. The pillowy alkyl ammonium bromide terminals at the upper side of the interlayer provide well‐matched growth sites for the perovskite, leading to mitigated interface strain and ensuing lattice distortion; meanwhile, its superior chemical compatibility presents an ideal effect on healing the under‐coordinated Pb atoms and halogen vacancies of bare perovskite crystals. The PASCA‐Br interlayer also serves as a mechanical buffer layer, inducing less cracked perovskite film when bending. The developed molecular‐level flexible interlayer provides a promising interfacial engineering for perovskite solar cells and their flexible application.

It is a challenge to grow perovskite films with large crystalline grains and a full coverage on the surface of an organic compound film by a solution process. Herein, we for the first time introduce environmental‐friendly urea into PbI2 precursor to mediate the perovskite film growth and crystallization on the top of PEODT:PSS for efficient inverted solar cells. This method attains high‐quality perovskite films with large‐size grains of over 2 μm and a full coverage. This enables us to fabricate the inverted perovskite solar cells showing a maximum efficiency of 18.01% with a fill factor of 82.29% and a stabilized efficiency of 17.56%. Infrared spectroscopy and scanning electron microscopy images demonstrate that urea is coordinated with PbI2 to form PbI2 · OC(NH2)2 complex, resulting in large PbI2 flakes by a slow crystallization. The large PbI2 flake with fewer nucleation sites is conducive to forming monolithic perovskite grains. Further investigation indicates that CH3NH3I · PbI2 · OC(NH2)2 complex is formed as an intermediate phase, which retards the crystallization process of the perovskite films. These factors lead to a high‐quality perovskite film with large grain size and excellent crystallinity.

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We report on the enhanced carrier injection in pentacene thin-film transistors with a thin MoO3-doped pentacene layer between pentacene semiconductor and the source-drain electrodes. Device performance including drain current, field effect mobility, and threshed voltage are improved by employing a MoO3-doped pentacene thin layer. The barrier height at the Au/pentacene interface is lowered from 0.12 to 0.05 eV after inserting a MoO3-doped pentacene thin layer between them. The reduced barrier height is attributed to the formation of a good contact between MoO3-doped pentacene and Au owing to smoothed surface morphology of pentancene and suitable band bending by MoO3 doping.