Unraveling the Operation Degradation Mechanism of Positive Bias Interface in Perovskite Solar Cells.

The interfaces of perovskite film are most susceptible to degradation during perovskite solar cell (PSC) operation. Previous efforts mainly focused on the degradation pathways of either independent upper or buried interfaces, while thorough and meticulous consideration of the disparity in electrical bias and light field difference between these interfaces during operation still remains unexplored. Herein, it is uncovered that the electrical bias significantly influences the operation degradation of perovskite interfaces in both n-i-p and p-i-n PSCs. More pronounced degradation has been found at the positive bias interface (perovskite/hole transporting layer interface) compared to the negative bias interface (perovskite/electron transporting layer interface). In the case of n-i-p PSCs, more severe degradation is mainly due to the electrochemical oxidation reaction catalyzed by diffused gold with high concentration of photogenerated holes at the positive bias interface. For p-i-n PSCs, the electrochemical oxidation reaction still occurs at the positive bias interface, inducing direct oxidation of silver with iodine species and photogenerated holes into silver iodide. Moreover, the incident light synergistically contributes to positive bias interface degradation in p-i-n PSCs. This work provides valuable guidance for understanding the degradation mechanism of different perovskite interfaces under different physical and chemical environment during device operation.