Simultaneous passivation of bulk and interface defects through synergistic effect of anion and cation toward efficient and stable planar perovskite solar cells

Bulk and interface carrier nonradiative recombination losses impede the further improvement of power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs). It is highly necessary to develop multifunctional strategy to minimize surface and interface nonradiative recombination losses. Herein, we report a bulk and interface defect passivation strategy via the synergistic effect of anions and cations, where multifunctional potassium sulphate (K2SO4) is incorporated at SnO2/perovskite interface. We find that K+ ions in K2SO4 diffuse into perovskite layer and suppress the formation of bulk defects in perovskite films, and the SO42– ions remain located at interface via the strong chemical interaction with SnO2 layer and perovskite layer, respectively. Through this synergistic modification strategy, effective defect passivation and improved energy band alignment are achieved simultaneously. These beneficial effects are translated into an efficiency increase from 19.45% to 21.18% with a low voltage deficit of 0.53 V mainly as a result of boosted open-circuit voltage (Voc) after K2SO4 modification. In addition, the K2SO4 modification contributes to ameliorated stability. The present work provides a route to minimize bulk and interface nonradiative recombination losses for the simultaneous realization of PCE and stability enhancement by rational anion and cation synergistic engineering.