Oriented Attachment of Tin Halide Perovskites for Photovoltaic Applications

Tin halide perovskites (THPs) are hopeful replacements to toxic Pb-based perovskites in lead-free photovoltaic applications. Nevertheless, the underlying crystallization kinetics mechanism lacks exploration to inform the rational design of high-quality THP films for the fabrication of optoelectronic devices. Here, we reveal a crystal growth kinetic regime for oriented attachment growth of THPs. By introducing 2-phenoxyethylamine bromide (POEBr) to tune the surface energy of different facets of FASnI₃ perovskite crystals, highly oriented FASnI₃-POEBr perovskite films are obtained. The crystalline films with anisotropic properties can be rationalized through the crystal growth kinetics mechanism called “oriented attachment (OA)”, where two smaller nanocrystals with the same crystallographical orientation combine together to produce a larger nanocrystal. The OA growth kinetics is amenable to reducing the crystal growth rate and consequently allows the formation of dense, smooth, and oriented THP films with fewer defects, delivering an impressive efficiency of over 14%.