Role of Moisture and Oxygen in Defect Management and Orderly Oxidation Boosting Carbon-Based CsPbI2Br Solar Cells to a New Record Efficiency

Large energy loss (E-loss) caused by defect-assisted recombination makes the photovoltaic performance of carbon-based perovskite solar cells (C-PSCs) inferior to that of metal-electrode ones. Herein, the influence of environmental factors (moisture and oxygen) on defect management during re-annealing process of CsPbI2Br crystalline films is systematically studied. Density functional theory and experimental results indicate that moisture in the air can significantly reduce the oxidation kinetics of crystalline films, resulting in orderly oxidation. Concomitantly, the oxidation decomposition products PbO and CsPbIBr2 are enriched at grain boundaries, passivating surface defects efficiently. Simultaneously, energy band coupling between CsPbI2Br and CsPbIBr2 improves the hole extraction efficiency. The photovoltage of corresponding C-PSCs is increased from 1.05 to 1.32 V, indicating a reduced E-loss derived from orderly oxidation strategy. Correspondingly, the champion cell achieves an efficiency of 15.27%, and a certified efficiency of 14.7%, which is a new record efficiency for CsPbI2Br C-PSCs.

Automated summary

Environmental factors such as moisture play a significant role in defect management during the re-annealing process of CsPbI2Br crystalline films. The presence of moisture reduces the oxidation kinetics and enables orderly oxidation, leading to improved photovoltaic performance in CsPbI2Br C-PSCs. The champion cell achieved a record efficiency of 15.27% in this study, highlighting the importance of defect management in enhancing the performance of carbon-based perovskite solar cells.