Defect Passivation of CsPbIBr₂ Perovskites for High-Performance Solar Cells with Large Open-Circuit Voltage of 1.28 V

As one of the all-inorganic perovskites, cesium lead mixed-halid perovskite (CsPbIBr2) has a bright photovoltaic application prospect owing to its ambient stability, appropriate bandgap, and distinctive color. However, the defect states in grain boundaries and the surface of CsPbIBr2 polycrystalline film lead to nonradiative carrier recombination which subsequently reduces the open-circuit voltage (VOC) and final power conversion efficiency (PCE) of the corresponding perovskite solar cells (PSCs). In this work, polyethylene glycol (PEG) is used to passivate the defect states of pure CsPbIBr2 film by improving the film morphology and coverage. The best-performance PSC based on PEG-passivated CsPbIBr2 exhibits a VOC of 1.28 V, a short-circuit current (JSC) of 8.80 mA cm–2, a fill factor (FF) of 0.649, and a PCE of 7.31%. However, the reference best-performance device based on pure CsPbIBr2 shows an inferior PCE of 6.36% with a lower VOC of 1.10 V, a comparable JSC of 8.81 mA cm–2, and a similar FF of 0.656. The VOC of 1.28 V is the highest among all CsPbIBr2 PSCs. Furthermore, the PEG-passivated PSC shows improved shelf stability in comparison with the reference device without PEG-passivation. This work provides a facile strategy to fabricate CsPbIBr2 PSCs with enhanced PCE, enlarged VOC, and improved stability by defect passivation.