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.

Elizabeth Guderjahn

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