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 (CsPbIBr 2 ) 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 CsPbIBr 2 polycrystalline film lead to nonradiative carrier recombination which subsequently reduces the open-circuit voltage ( V OC ) 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 CsPbIBr 2 film by improving the film morphology and coverage. The best-performance PSC based on PEG-passivated CsPbIBr 2 exhibits a V OC of 1.28 V, a short-circuit current ( J SC ) 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 CsPbIBr 2 shows an inferior PCE of 6.36% with a lower V OC of 1.10 V, a comparable J SC of 8.81 mA cm –2, and a similar FF of 0.656. The V OC of 1.28 V is the highest among all CsPbIBr 2 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 CsPbIBr 2 PSCs with enhanced PCE, enlarged V OC, and improved stability by defect passivation.