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

The alpha -> delta phase transition, which occurs favorably in planar films of a black alpha-HC(NH2)(2)PbI3 (alpha-FAPbI(3)) perovskite in the amibent, is retarded when alpha-FAPbI(3) is deposited upon mesoporous TiO2 scaffolds. It is hypothesized that this is due to the synergistic effect of the partial encapsulation of alpha-FAPbI(3) by the mesoporous TiO2 and the elevated activation energy for the transition reaction associated with the substantial increase of the TiO2/alpha-FAPbI(3) interfacial area in the mesoscopic system.