500+ FACs Perovskite Solar Cells under Long-Term Stability Testing

The long-term stability of more than 500 FACs perovskite solar cells has been systematically investigated under various conditions. We first analyze resilience to moisture and show that with the 30 nm Al₂O₃ capping, we can perform long-term tests in air and eliminate moisture-related degradation. In the long-term MPP tracking tests, we then confirm that light is the driving degradation contributor by performing cyclic tests and testing under different light intensities. Visual changes of the perovskite absorber during the testing and spatial and spectral photoluminescence measurements reveal that phase segregation and the perovskite/C₆₀ interface are the main culprits for degradation, while the perovskite degrades faster in electrically inactive areas. We thus show that by removing bromide ions from the FACs composition, cell stability, evaluated by the t₈₀ lifetime, can improve 5-fold in the best case and that there is a linear correlation between t₈₀ time and bias voltage during stability tracking. By testing a large number of samples (>500), we show with statistical relevance that long-term stability measurements show significantly higher spread (both batch-to-batch and intrabatch) than J-V measurements.