Electronic and optical properties of potential solar absorber Cu3PSe4
  We theoretically investigate the electronic and optical properties of semiconductor Cu3PSe4. We also report diffuse reflectance spectroscopy measurements for Cu3PSe4 and Cu3PS4, which indicate a band gap of 1.40 eV for the former.Hybrid functional calculations agree well with this value, and reveal that the band gap is direct. Calculations yield an optical absorption spectrum similar to GaAs in the visible region, with {\alpha} > 5x10^4 cm^-1 for {\lambda} < 630 nm. We conclude that the optical properties of Cu3PSe4 are within the desired range for a photovoltaic solar absorber material. 
D. H. Foster, V. Jieratum, R. Kykyneshi, D. A. Keszler, and G.   Schneider
cond-mat.mtrl-sci