Self‐Trapped Excitons in 2D SnP2S6 Crystal with Intrinsic Structural Distortion

Abstract Exploring and utilizing novel materials with self‐trapped excitons (STEs) is highly desired due to their unique physical properties and multiple optoelectronic applications. Here, a 2D SnP 2 S 6 crystal is reported with obvious STEs emission caused by distorted [SnS 6 ] 8‐ and [P 2 S 6 ] 4‐ octahedral units and strong electron‐phonon coupling. The STEs feature wide photoluminescence (PL) spectra range from 600 to 850 nm and a large Stokes redshift of ≈0.6 eV. Carrier dynamics measurements including temperature‐dependent PL and transient absorption reveal a large Huang–Rhys factor of ≈18.3 and a self‐trapping process of ≈10 1 –10 3 ps in the 2D SnP 2 S 6 crystal. Such self‐trapped states enable 2D SnP 2 S 6 crystal a wide spectral response range and excellent photodetection performance. As a result, high responsivity (22.8 A W ‐1 ) and detectivity (3.98 × 10 10 Jones) are achieved under 365 nm light illumination. These results provide a deep insight into the photophysical process of STEs, which lays the foundation for developing novel STEs‐based materials and optoelectronic devices.