Degradation Pathway Tailoring through Nanocrystal Interface Engineering for Photostable Perovskite Solar Cells

While organic–inorganic hybrid perovskites (ABX₃) hold immense photovoltaic potential, operational instability originating from defect-mediated ion migration and light-induced degradation remains a critical bottleneck. Here, we adopt Cs₂PbI₂Cl₂ nanocrystals (CPIC-NCs) and CsPbCl₃ nanocrystals (CPC-NCs) to modify the interface of the perovskite light-absorbing layer. Beyond conventional defect-healing roles (Cs⁺/halide filling of the A/X-site vacancies), this modification can fundamentally alter the degradation pathways of perovskite films under light exposure. Our study reveals CPIC-NCs serve as a superior modifier by inducing a more controllable formation of Pb(OH)I and effectively suppressing the decomposition of perovskite into lead iodide after long-term light aging. Following the CPIC-NCs modification of the solar cells, a champion power conversion efficiency of 24.28% was achieved. Moreover, the unencapsulated devices retained over 90% of their initial efficiency after 600 h under ISOS-L-1I and 4500 h under ISOS-D-1 conditions. This work establishes nanocrystal-mediated interface control as a dual-defect/degradation regulatory strategy for perovskite optoelectronics.