Polymer‐wrapped Perovskite Single Crystal for Surface Passivation and Robust Stability

Metal halide perovskites (MHPs) emerging as a promising semiconducting material have shown superiority in optoelectronic applications. Currently, polycrystalline perovskite thin films are dominantly employed; while owing to the existence of grain boundary, the polycrystalline films typically have charge transport issues. To overcome these limitations, a perovskite single crystal (SC) is synthesized and applied owing to the more superior bulk charge transport properties compared with its polycrystalline counterpart. Nevertheless, due to the defective nature of the crystal surface, the surfaces of single crystals remain the bottleneck that not only induces stability issues but also causes interfacial charge carrier recombination. In this work, triple cation perovskite single crystals, FA(0.8)MA(0.15)Cs(0.05)PbI(3) (denoted as FAMACs) are synthesized, and a facile surface modification strategy is reported for single crystals by polymer monolayer coupling, which shows high effectiveness for improving stability and reducing surface trap state density for single crystals. The polymer-wrapped single crystals exhibit robust stability and a well-passivated surface, which shows an order of magnitude lower trap density compared with those of unmodified single crystals and achieves a high responsivity of 5.069 A W-1 when used in photodetector applications.