Oxygen vacancy defects are a source of the n-type self-doping effect in SnO2 and determine the electron mobility of SnO2. However, during the synthesis of SnO2 colloidal nanoparticles or the deposition of films, the spontaneously formed intrinsic oxygen vacancy will act as charge trap states at the surface and interfaces, which significantly influence the electrochemistry properties of SnO2. In this study, a defect modulation strategy was proposed to synthesize SnO2 quantum dot solution at an oxygen atmosphere to lower oxygen vacancy defects and further dope with PbBr2 to compensate the carrier density, thereby increasing the electron mobility and promoting efficient charge transport. Through UV-O3 treatment, PbBr2 was partially oxidized to PbO2, while unoxidized PbBr2 acted as a pre-embedded precursor to form an interpenetrating interface. It regulates the perovskite crystallization and reduces the residual stresses. The defect modulation achieves an efficiency of 10.24% with an ultrahigh fill factor of 87.63% for carbon-based CsPbBr3 perovskite solar cells and 24.05% for the FAPbI3-based device.
Liu et al. (Wed,) studied this question.