Defect-Modulated Synthesis of SnO₂ for Carbon-Based CsPbBr₃ Perovskite Solar Cells

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.