Growth of large CH3NH3PbX3 (X=I, Br) single crystals in solution

• Growth of large CH3NH3PbX3 single crystals.
• Structural phase transition observed.
• Crystal solubility determined.

We present the results on the successful growth of CH3NH3PbX3 (X=I, Br) single crystals sized up to centimeters using hydrohalic acid solution method. Large crystals with perfect morphology were obtained by a very slow cooling rate of 0.1–0.2 °C/h. The lattice parameters of tetragonal CH3NH3PbI3 and cubic CH3NH3PbBr3 were estimated using the Rietveld refinement method. Study of crystal nucleus, habits and dimensions indicates that these are strongly dependent on the supercooling of solution during crystal growth, in which the (0 0 1)/(0 1 0) for CH3NH3PbI3 and {1 0 0} for CH3NH3PbBr3 always exhibit the largest faces on the as-grown crystals. A structural phase transition of tetragonal/cubic and cubic/tetragonal for the CH3NH3PbI3 single crystals was observed to occur at 62 and 60 °C during the heating and cooling process, respectively. The nonlinear relationship of temperature-dependent solubility for CH3NH3PbI3 in hydrohalic acid was also determined.