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

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 Cs 3 Cu 2 I 5 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 Cs 3 Cu 2 I 5 perovskite films are investigated. Even though the Cs 3 Cu 2 I 5 perovskite films prepared with or without anti-solvent demonstrate the same crystal structure of the orthorhombic phase, by the anti-solvent approach, Cs 3 Cu 2 I 5 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, Cs 3 Cu 2 I 5 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 Cs 3 Cu 2 I 5 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.