Theoretical Photovoltaic Conversion Efficiencies of ZnSnP2, CdSnP2, and Zn1-xCdxSnP2 Alloys

The performances of ZnSnP2, CdSnP2, and Zn1-xCdxSnP2 alloys as solar cell photoabsorbers are assessed using photovoltaic conversion efficiency simulations in conjunction with first-principles calculations based on hybrid density functional theory. The band gap of Zn1-xCdxSnP2 decreases with increasing Cd content x and shows a small bowing. The electronic structure and optical absorption spectrum depend weakly on the composition, aside from the band gap and spectral threshold. The conversion efficiency is almost converged to the Shockley-Queisser limit at a photoabsorber thickness of a few micrometers for any composition of Zn1-xCdxSnP2, similarly to the cases of GaAs, CdTe, CuInSe2, and CuGaSe2. (C) 2013 The Japan Society of Applied Physics