Revealing the Relationship between Interfacial Morphology Degradation and Unsatisfied Stability in Phenethylamine‐Treated Perovskite Solar Cell

Abstract The surface passivation with phenethylammonium halides has proven effective in reducing defect density and trap‐assisted recombination, enabling outstanding efficiency in perovskite solar cells. Despite its promise, it is ambiguous whether this strategy can improve the stability of devices under rigorous conditions, such as light soaking and thermal aging. A critical issue is whether the interface is robust in structure and morphology under light illumination. Here, a dynamical morphology mutation of the passivated perovskite interface under continuous light irradiation is uncovered, and propose a possible mechanism. The surface passivation is unstable under light stress, leading to the generation of defects, accumulation of photoexcited carriers, and migration of halide ions. Additionally, the chemical reaction between the passivation layer and organic species/PbI ₂ leads to the loss of volatile gas and organic species. These processes deteriorate interfacial morphology, producing numerous pinholes and accelerating stability degradation. In conclusion, morphological degradation is the leading cause limiting the operational stability of passivated devices. To mitigate this issue, it is suggested that it is imperative to construct a robust interface structure through preventing direct contact between the passivation layer and perovskite or employing other passivation.