Understanding the Long-Term Instability in Perovskite Solar Cells: Mechanisms and Mitigation Strategies

Power conversion efficiency (PCE) of single-junction perovskite solar cells (PSCs) has already soared from 3.8% to more than 26%. Their potential for application in tandem architecture with silicon and other established solar technologies has been deemed the future of low-cost solar technology. However, the commercialization of this technology is critically limited by instability under operational and environmental stress. The instability in the PSCs stems from both internal mechanisms including ion migration, defect formation, and electrode or charge transport layer (CTL)-induced degradation as well as external stressors such as moisture, oxygen, heat, and illumination. A complete understanding of both the internal and external stimuli-induced degradation and their mitigation strategies is essential for improving the device’s longevity. This review aims to provide a complete overview of the degradation mechanisms and steps taken to mitigate the degradation issues. The first half of the review discusses the degradation mechanism caused by internal degradation factors and provides strategies to mitigate them, while the second half focuses on the external stressors and the approaches developed by the perovskite community to overcome them. The commercialization of PSCs will depend on a holistic approach that simultaneously ensures both intrinsically as well as extrinsically stable devices.