Revisiting thiophosphate $Pb_3P_2S_8$: A multifunctional material combining a nonlinear optical response and photocurrent response

Abstract

$Pb_3P_2S_8$ was structurally characterized three decades ago with a second harmonic generation response. In this work, $Pb_3P_2S_8$ 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. $Pb_3P_2S_8$ is constructed by $[PbS_7]$ polyhedra and $[PS_4]$ 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. $Pb_3P_2S_8$ 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. $Pb_3P_2S_8$ 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). $Pb_3P_2S_8$ exhibits an intriguing photocurrent response of 45 μA cm−2 under light irradiation. $Pb_3P_2S_8$ is a new multifunctional material combining a nonlinear optical response and photocurrent response.