Cesium Decreases Defect Density and Enhances Optoelectronic\nProperties of Mixed MA_1–<i>x</i>Cs<i>_x</i>PbBr₃ Single Crystal

Abstract

The existence of\nthe organic component (MA) in MAPbBr₃ guarantees its cubic\ncrystal lattice stabilities to satisfy the\ntolerance factor but increases the chemical instability risk when\nencountering moisture, oxidation, and heat. Mixed cations, particularly\nwhen using cesium cation (Cs⁺), prove to be an effective\nway of improving both stability and optoelectronic performances of\nhybrid perovskite films applied in solar cells. However, the intrinsic\neffect of Cs⁺ on the crystal structure, lattice defects,\nand optoelectronic properties of MAPbBr₃ is still unclear\ntill now because grain boundary numbers and interface defect densities\nin films increase complexity; so, it is not easy to explore the intrinsic\nnature of how Cs⁺ affects the optoelectronic properties\nof MAPbBr₃. Single crystals (SCs) of MAPbBr₃ provide an ideal medium to investigate the influence of Cs⁺ on the crystal structure and optoelectronic performances. Herein,\nwe grew a series of MA_1–<i>x</i>Cs<i>_x</i>PbBr₃ SCs. This reveals that Cs⁺ inhibits the growth of MAPbBr₃ SCs, causes crystal\nlattice shrinkage, decreases crystal defects, and therefore reduces\nthe dark currents, decreases the trap densities, and optimizes the\noptoelectronic properties. Our work provides a reference for the relationship\nbetween the composition of the mixed lead halide perovskites and the\noptoelectronic properties.