Observation of phase-retention behavior of the HC(NH2)2PbI3 black perovskite polymorph upon mesoporous TiO2 scaffolds

Abstract

The α → δ phase transition, which occurs favorably in planar films of a black α-HC(NH₂)₂PbI₃ (α-FAPbI₃) perovskite in the amibent, is retarded when α-FAPbI₃ is deposited upon mesoporous TiO₂ scaffolds. It is hypothesized that this is due to the synergistic effect of the partial encapsulation of α-FAPbI₃ by the mesoporous TiO₂ and the elevated activation energy for the transition reaction associated with the substantial increase of the TiO₂/α-FAPbI₃ interfacial area in the mesoscopic system.