Bismuth Doping Alters Structural Phase Transitions in Methylammonium Lead Tribromide Single Crystals

We study the effects of bismuth doping on the crystal structure and phase transitions in single crystals of the perovskite semiconductor methylammonium lead tribromide, MAPbBr(3). By measuring the temperature-dependent specific heat capacity (C-p), we find that as the Bi doping increases, the phase transition assigned to the cubic to tetragonal phase boundary decreases in temperature. Furthermore, after doping we observe one phase transition between 135 and 155 K, in contrast to two transitions observed in the undoped single crystal. These results appear strikingly similar to previously reported effects of mechanical pressure on perovskite crystal structure. Using X-ray diffraction, we show that the lattice constant decreases as Bi is incorporated into the crystal, as predicted by density functional theory. We propose that bismuth substitutional doping on the lead site is dominant, resulting in Bi-Pb(+) centers that induce compressive chemical strain that alters the crystalline phase transitions.

Automated summary

Bismuth doping has effects on the crystal structure and phase transitions of the perovskite semiconductor MAPbBr(3). The phase transition temperature decreases and the number of phase transitions decreases with increasing Bi doping. X-ray diffraction shows that lattice constant decreases with Bi incorporation, suggesting dominant bismuth substitutional doping on the lead site.