Extrinsic Dual-Mode Self-Trapped Excitons Emission With Highly Linear Polarization From Cu3PS3Se

Abstract

Benefiting from the potential application as a single component white light source, the broadband self-trapped excitons (STEs) emission in low-dimensional metal halides has attracted wide attention. However, such broadband STE emission in metal thio- and seleno-phosphates is scarce, and the formation mechanism is ambiguous. Herein, the broadband dual-mode (red and near-infrared) light emission and their linear polarization in orthorhombic Cu₃PS₃Se crystals are reported. The absorption and photoluminescence (PL) spectra show a large Stokes shift of 0.43/0.76 eV and a broad emission wavelength range of ≈200 nm, exhibiting the significant STEs feature. Transient absorption spectroscopy (TAS) reveals a broad positive photo-induced absorption, further proving the formation of STE states. These STEs exhibit a highly linear polarized emission behavior with a degree of polarization up to 0.51. According to the excitation angles dependent polarized PL and Raman spectroscopy measurements, it is assigned that both the anisotropic optical absorption and electron-phonon interaction contribute to the STEs emission polarization in Cu₃PS₃Se. These findings not only extend the STEs from metal halides to metal thio/seleno-phosphates but also offer the potential prospects for novel optical polarizers, polarization-sensitive photodetectors, optical and optoelectronic synaptic devices application of anisotropic STEs emission.