Surface Defect Clipping Strategy Enables High-Efficiency Inorganic Perovskite Solar Cells with Ultralow <i>V</i>_OC Deficit

Recent developments in perovskite-silicon tandem solar cells (TSCs) have been quite remarkable. Inorganic perovskite solar cells (IPSCs) are gradually emerging as the top cells in the tandem device. However, IPSCs generally suffer from a severe open-circuit voltage (VOC) deficit, limiting their efficiency gains and application in TSCs. Here, we developed a surface defect clipping strategy using pyridyl-2,6-dicarboxamide (PD) in a methanol solution. The proper polarity of the methanol solution will clip the upper surface of the inorganic perovskite film and provide a corresponding path for penetration of the PD solution. In addition, PD efficiently in situ passivate uncoordinated Pb2+. After the annealing, dense perovskite films were formed on the upper surface of the inorganic perovskite. The crystallization dynamics of inorganic perovskites near the surface is regulated, and nonradiative recombination is effectively suppressed. Eventually, a record VOC of 1.259 V (1.71 eV) is achieved based on inverted IPSCs, and the VOC deficit is only 450 mV. More importantly, unencapsulated IPSC devices show significantly enhanced thermal and humidity stability.