Cesium Decreases Defect Density and Enhances Optoelectronic Properties of Mixed MA1–xCsxPbBr3Single Crystal

The existence of the organic component (MA) in MAPbBr3guarantees its cubic crystal lattice stabilities to satisfy the tolerance factor but increases the chemical instability risk when encountering moisture, oxidation, and heat. Mixed cations, particularly when using cesium cation (Cs+), prove to be an effective way of improving both stability and optoelectronic performances of hybrid perovskite films applied in solar cells. However, the intrinsic effect of Cs+on the crystal structure, lattice defects, and optoelectronic properties of MAPbBr3is still unclear till now because grain boundary numbers and interface defect densities in films increase complexity; so, it is not easy to explore the intrinsic nature of how Cs+affects the optoelectronic properties of MAPbBr3. Single crystals (SCs) of MAPbBr3provide an ideal medium to investigate the influence of Cs+on the crystal structure and optoelectronic performances. Herein, we grew a series of MA1–xCsxPbBr3SCs. This reveals that Cs+inhibits the growth of MAPbBr3SCs, causes crystal lattice shrinkage, decreases crystal defects, and therefore reduces the dark currents, decreases the trap densities, and optimizes the optoelectronic properties. Our work provides a reference for the relationship between the composition of the mixed lead halide perovskites and the optoelectronic properties.