Fundamental Optical Constants and Anti-Reflection Coating of Melt-Grown, Polished CsPbBr₃ Crystals

Lead halide perovskites are notorious for water-sensitivity and low hardness. Consequently, polishing CsPbBr₃ crystals to achieve high-quality surfaces is challenging. We present a breakthrough mechanical polishing methodology tailored to the specific needs of these soft, moisture-sensitive semiconductors. Three-dimensional optical surface profiles over ~1 mm² areas demonstrate high-quality surfaces with root-mean-square roughness values (<10 nm) that are unparalleled for melt-grown CsPbBr₃. We additionally delve into the polished wafers’ fundamental optical constants and introduce an anti-reflection coating method, setting new standards for short-wave infrared transparency in CsPbBr₃. These pivotal processing guidelines pave the way for advancing halide perovskite applications beyond academic curiosity.