Enhancing Ultraviolet Stability and Operational Durability of Perovskite Photodetectors by Incorporating Chlorine into Thermally-Switchable Tautomeric Passivators

• The tautomeric UV absorbers (UV320/UV327) in perovskites reveal keto–enol tautomerism, generating extra –C=O groups to enhance defect passivation. • The Cl atom in UV327 drives tautomerism, providing superior –C=O coordination, which optimizes SnO2 energy bands/charge extraction, resulting in a dark current of 3.22 × 10−10 A cm−2 and a response time of 23.35/26.19 μs. • Unencapsulated devices maintained 3900 Hz response after 300 h humidity (40 ± 5% RH) and 30 h UV stress, with 94.14 dB linear dynamic range. • The study provides a mechanistic understanding of tautomeric passivators and demonstrates a strategy for enhancing UV stability and operational durability of perovskite photodetectors.