Green anti-solvent assisted crystallization strategy for air-stable uniform Cs3Cu2I5 perovskite films with highly efficient blue photoluminescence

Abstract

Metal halide perovskites have aroused extensive attention due to their excellent photoelectric properties. But the toxicity and instability of lead-based perovskite restrict their development severely. Recently, lead-free Cu-based perovskites have emerged as promising environmental friendly photoelectric materials on account of their low toxicity and equally excellent properties. Here, we report the highly uniform lead-free Cs3Cu2I5 perovskite films with the long-term air-stability prepared by using methyl acetate as anti-solvent during the fabrication. The crystal structure, surface morphology, bandgap, and optical property of the Cs3Cu2I5 perovskite films are investigated. Even though the Cs3Cu2I5 perovskite films prepared with or without anti-solvent demonstrate the same crystal structure of the orthorhombic phase, by the anti-solvent approach, Cs3Cu2I5 perovskite films exhibit an enhanced photoluminescence quantum efficiency (PLQY) from ~62% to ~76.0% and have a relatively smaller surface roughness ~17.5 nm. Most importantly, Cs3Cu2I5 perovskite films exhibited long-term air-stability, and the PLQY could still reach 76.3% after storing for several months under an ambient atmosphere. All the results demonstrate the quality and the PLQY of Cs3Cu2I5 perovskite films could be effectively improved by the anti-solvent assisted crystallization strategy, showing potential applications in the fabrication of photoelectric devices based on lead-free perovskites.