Shape-controlled synthesis of organolead halide perovskite nanocrystals and their tunable optical absorption

Hybrid organolead halide perovskites (CH3NH3PbI3) with polymorphic structures have been successfully synthesized by controlling their solubility in solvents with different polarities. Crystal formation stages of the perovskites have been demonstrated for the first time. Shape changes of such perovskites are accompanied by transition in their crystal structures and variation of optical properties. Herein, a new trigonal phase for CH3NH3PbI3 has been observed with a rod-like morphology. Photoemission study indicates a significant red shift in the perovskite nanoparticles, compared to that of the rod-like nanocrystals. This solvent-controlled formation of polymorphic phases provide an additional approach for controlling the optical properties of CH3NH3PbI3 for various optoelectronic applications.