Self‐Trapped Excitons in 3R ZnIn2S4 with Broken Inversion Symmetry for High‐Performance Photodetection

Abstract Exploring novel materials with intrinsic self‐trapped excitons (STEs) is crucial for advancing optoelectronic technologies. In this study, 2D 3R‐phase ZnIn 2 S 4 , featuring broken inversion symmetry , is introduced to investigate intrinsic STEs. This material exhibits a broadband photoluminescence (PL) emission with a full width at half maximum of 164 nm and a large Stokes shift of ≈0.6 eV, which arises from the distortion of [ZnS 4 ] 6‐ tetrahedral unit induced by the symmetry breaking and strong electron‐phonon coupling. The photophysical properties of the STEs exhibit a high Huang‐Rhys factor (15.0), rapid STEs formation time (166 fs), and extended STEs lifetime (1039 ps), as demonstrated by experimental evidence from temperature‐dependent PL, Raman spectroscopy, and ultrafast absorption spectroscopy. Additionally, STE‐induced photoconductive effect is elucidated, indicating that intrinsic STEs in 3R‐ZnIn 2 S 4 can provide a synergistic effect that enhances absorption capacity, localization, and lifetime by capturing the self‐trapped hole state. Consequently, the 2D 3R‐ZnIn 2 S 4 photodetector exhibits remarkable broad‐spectrum photosensitivity, including a photo‐switching ratio of 11286, response times of less than 0.6 ms, responsivity of 15.2 A W −1 , detectivity of 1.02 × 10¹¹ Jones, and external quantum efficiency of 5032% under 375 nm light. These findings provide new ideas for exploring materials with intrinsic STEs to achieve novel high‐performance photodetector applications.