Strain Regulation Attenuates Natural Operation Decay of Perovskite Solar Cells

Perovskite solar cells (pero-SCs) have undergone a rapid development in the last decade. However, there is still a lack of systematic studies to investigate whether the empirical rules used in silicon solar cells working lifetime assessment can be applied to pero-SCs. It is commonly believed that pero-SCs show enhanced stability under day/night cycling due to the reported self-healing effect in the dark. In our research, it is discovered that the degradation of highly efficient FAPbI₃ pero-SCs is in fact much faster under natural day/night cycling mode, questioning the widely accepted approach to estimate the pero-SCs’ operational lifetime based on continuous mode testing. We reveal the key factor to be the lattice strain during the operation, an effect that gradually relaxes under the continuous illumination mode but cycles synchronously under the cycling mode. The periodic lattice strain under the cycling mode results in deep trap accumulation and chemical degradation during operation, decreasing the ion migration potential and hence the device lifetime. We introduce phenylselenenyl chloride (Ph-Se-Cl) to regulate the perovskite lattice strain during day/night cycling, which achieved the certified efficiency of 26.3% and a 10-time improved <i>T</i>₈₀ lifetime under the cycling mode after the modification.