Revisiting thiophosphate Pb3P2S8: a multifunctional material combining a nonlinear optical response and photocurrent response

Abstract

Pb₃P₂S₈ was structurally characterized three decades ago with a second harmonic generation response. In this work, Pb₃P₂S₈ was revisited to investigate its electronic structure via DFT calculations and optical properties by UV-vis measurements, second harmonic generation tests, laser damage threshold tests, and photocurrent measurements. Pb₃P₂S₈ is constructed by [PbS₇] polyhedra and [PS₄] tetrahedra, which was supported by crystal orbital Hamilton population (COHP) calculations. The electron localization function (ELF) simulations revealed the dominantly covalent and ionic bonding nature of P–S interactions and Pb–S interactions, respectively, both of which are strongly polarized. Pb₃P₂S₈ is an indirect n-type semiconductor of 1.8 eV and 2.4(1) eV, which are obtained from DFT calculations and UV-vis measurements, respectively. Pb₃P₂S₈ is a non-type-I phase matching material with a good balance of second harmonic generation (SHG) and laser damage threshold (LDT) of 3.5 × AGS and 2.6 × AGS, respectively (SHG based on 38–50 μm particle size sample). Pb₃P₂S₈ exhibits an intriguing photocurrent response of 45 μA cm⁻² under light irradiation. Pb₃P₂S₈ is a new multifunctional material combining a nonlinear optical response and photocurrent response.