Phenethylammonium bismuth halides: from single crystals to bulky-organic cation promoted thin-film deposition for potential optoelectronic applications

Bismuth-based organohalides have attracted much attention as potential alternatives to lead halide perovskites and have been explored in various electronic and optoelectronic devices. Developing new bismuth organohalides with rational design has been a dynamic research area. Herein, we developed single-crystals and thin-films of a new class of bismuth-based organohalides (phenethylammonium (C8H12N+, PEA+) bismuth halides). We found that comparable optical properties can be preserved after replacing methylammonium with bulky PEA+ cations. The bulky PEA+ cation significantly promotes the coverage and low surface roughness of bismuth organohalide thin-films in a facile one-step solution method. Newly-prepared (PEA)3Bi2I9 also shows excellent thermal and humidity stability, showing promise for addressing the toxicity and stability of optoelectronic/electronic devices beyond lead halide perovskites.