Some of the thiophosphates screened by Han and Ebert have been experimentally investigated. Tiwari et al. studied the optoelectronic properties of BiPS 4 powders for solar energy conversion. BiPS 4 , a 3D PS, was found to have a direct band gap of 1.72 eV, n-type conductivity, moderate electron effective masses, and an encouraging carrier lifetime around 1 ns. Shaddad et al. utilized a BiPS 4 /BiVO 4 heterojunction to increase the photocurrent of a bare BiVO 4 photoanode for PEC water splitting. The Cu 3 PS 4-x Se x solid-solution series (3D) was synthesized in powder form by , and investigated as a potential PV absorber. With increasing sulfur content, the band gap increased from 1.35 eV (Cu 3 PSe 4 ) to 2.38 eV (Cu 3 PS 4 ). This band gap range covers the requirements of many optoelectronic energy conversion technologies. Spectrally narrow photoluminescence close to the band gap energy and a PEC response were subsequently measured for pure-sulfide Cu 3 PS 4 nanoparticles, which were also employed as a hole transport layer in perovskite solar cells. The optoelectronic properties of the 2D PS GaPS 4 were computationally investigated by two groups. Liu et al. predicted a reduction of the band gap and improved band alignment for unassisted PEC water splitting upon introduction of single transition metal atoms into GaPS 4 . Shen et al. performed defect calculations in GaPS 4 to derive favorable growth conditions for n-and p-type doping. Furthermore, they found that a higher optical band gap in GaPS 4 compared to the fundamental calculated band gap is due to dipole-forbidden transitions. This feature was independently found in Ag 3 PS 4 , despite the substantially different structures in the two compounds. Pd 3 (PS 4 ) 2, another 2D PS material with [PS 4 ] 3-anions, was experimentally studied by Roy et al., who reported a PEC response from exfoliated nanosheets of this material. A few 2D thiophosphates with [P 2 S 6 ] 4-anions have also been optoelectronically characterized to a limited extent. In 1979, Brec et al. characterized MPS 3 crystals and powders (M= Mn, Fe, Ni, Zn, Cd, In 0.66 ) and reported their band gaps (1.5-3.5 eV), electrical resistivity (10 2 -10 4 Ωcm) and α (exceeding 10 4 cm -1 just above the fundamental band gap). These materials were also computationally examined by Zhang et al. for PEC applications. The authors calculated their band alignment and optical absorption coefficient, and concluded that FePS sheets in PEC cells, and observed an increased photocurrent when oxygen was incorporated on the CuInP 2 S 6 surface. We could only find a single, very recent study on the optoelectronic properties of a [P 2 S 7 ] 4-thiophosphate (Feng et al. ). Using first-principles calculations, the authors concluded that two different phases of Ag 4 P 2 S 7 possess high α in the visible and suitable band edge positions for PEC water splitting. Moving to non-thiophosphate PSs with P/S = 1, Roy et al. demonstrated working photodetectors based on exfoliated PdPS sheets. Houari and Benissad suggested CoPS as a PV absorber based on first-principle calculations. As mentioned in Section 2.1, it appears that no materials with P/S > 1 have been synthesized in any form. However, the available on the MP database, to account for their systematic underestimation. The corrected values are obtained by polynomial regression between the PBE band gaps and the more accurate band gaps calculated at the HSE06 level on a sample of 62 PSs available in the SNUMAT database .