Single-Crystal Growth and Thermal Stability of (CH3NH3)1-xCsxPbBr3

We describe the growth of single crystals of the halide perovskites APbBr(3), with varying ratios of Cs to methylammonium (MA) on the A site, by antisolvent vapor-assisted crystallization (AVC) and characterize the structural and compositional homogeneity of the grown crystals. We find improved thermostability for the Cs-rich mixed crystals and suggest that this is caused by a combination of locking-in of the relatively large MA in the smaller lattice of the Cs-rich material as well as by stronger hydrogen bonding between the nitrogen of MA and Br due to reduced lattice size and/or octahedral tilting with increased Cs. We also show that it is possible to grow either compositionally homogeneous crystals or core-shell, compositionally graded crystals by changing the ratio of antisolvent to solvent in the AVC method.