A Visible and NIR Light‐Driven Photoswitch With High Fluorescence On/Off Contrast and Near‐Quantitative Cyclization Yield for Photonic Applications

Abstract Fluorescent dithienylethene (DTE) photoswitches show significant potential for applications in optical data storage, super‐resolution imaging, high‐security anti‐counterfeiting and information encryption. Nevertheless, the current systems remain constrained by several fundamental limitations, including dependence on higher‐energy excitation for photocyclization, suboptimal photoswitching kinetics, limited fluorescence modulation contrast, and incomplete ring‐closure conversion. Herein, a novel dithienylethene photoswitch (CDBT) featuring a donor‐DTE‐acceptor‐donor (D‐DTE‐A‐D') architectural motif has been rationally designed and synthesized, where the N‐phenylcarbazole and thiophene groups represent two donors (D and D'), respectively, and difluoroboron β ‐diketonate moiety serves as the acceptor (A). Leveraging The sophisticated “acceptor synergistic conjugation system” strategy, CDBT remarkably demonstrates fast photoswitching kinetics, near‐quantitative cyclization yield (up to 96.6%), exceptional fluorescence ON/OFF ratio of 2300:1 and multicolor fluorescence switching behavior within 5 seconds of irradiation with long‐wavelength green light. The proof‐of‐concept applications in information encryption, anti‐counterfeiting, and photorewritable patterns are successfully demonstrated exclusively using green/near‐infrared light. This work opens a new avenue for developing high‐performance DTE photoswitches triggered by longer‐wavelength visible light.