Radiative Recombination Changes under Light-Soaking in CsPbBr3 Films on TiO2 and Insulating Glass Contacts: Interface versus Bulk Effects

The steady-state photoluminescence (PL) of CsPbBr3 films with varying thicknesses was studied under light-soaking on semiconductive and insulating contacts, showing reversible changes in PL, entirely dependent on the nature of the contact and film thicknesses. The PL at 50-100 nm CsPbBr3 on TiO2 increased, and decreased in thicker layers, with no thickness-dependent PL in CsPbBr3 on glass/Al2O3. These observations are described using a spatial charge distribution model which interprets the migration of Br- and V-Br(+) under light-soaking as suppressing electron injection into the TiO2 due to upward band bending, enhancing PL at the interface and nonradiative recombination further away from it.