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

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 SnP2S6 crystal is reported with obvious STEs emission caused by distorted [SnS6](8-) and [P2S6](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 approximate to 0.6 eV. Carrier dynamics measurements including temperature-dependent PL and transient absorption reveal a large Huang-Rhys factor of approximate to 18.3 and a self-trapping process of approximate to 10(1)-10(3) ps in the 2D SnP2S6 crystal. Such self-trapped states enable 2D SnP2S6 crystal a wide spectral response range and excellent photodetection performance. As a result, high responsivity (22.8 A W-1) and detectivity (3.98 x 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.