Dynamic Photochromic Switching Enables Efficient and UV-Resistant Perovskite Solar Cells

Ultraviolet (UV) irradiation is one of the key factors affecting the stability of perovskite solar cells (PSCs), yet completely shuttering UV light would degrade the current output of the devices. Thus improving UV stability without loss of current generation remains challenging to date. Herein, we report a simple methodology by incorporating a photochromic diarylethene (6F) molecule into the perovskite film, which simultaneously improves the efficiency and UV stability of PSCs. We unearth two distinct degradation routes for PSCs under UV irradiation: perovskites into precursor components or the α-phase to δ-phase transition, followed by decomposition into precursor components. We further reveal that the dynamic photochromic effect of 6F under irradiation induces UV protection of the perovskite film by completely shutting down the latter route, which significantly improves the UV stability of PSCs. Additionally, hydrogen bonding between 6F and perovskite lead to the passivation of defects in the lattice, eventually giving a power conversion efficiency (PCE) of 24.18% compared with the control device (22.14%), which is among the highest PCEs for inverted PSCs via a two-step solution method. We believe this methodology can offer a new avenue toward fabricating efficient and stable PSCs.