Design and study of SrSnX2 (X=N, P, Sb, As, Bi) semiconductors using density functional theory

Abstract

A series of novel, low-cost materials SrSnX2 (X=N, P, Sb, As, Bi) is explored through density functional theory in terms of structural, electronic, and optical properties to underline the usage of these compounds as photo-absorber materials. Within the modified Becke-Johnson exchange-correlation potential, SrSnN2 shows a direct band gap of 1.94 eV while other materials in the series show a natural intermediate band which supports the two-step optical transition and hence increases the absorption in the visible energy region. Calculated values of the effective mass of electrons, effective densities of conduction, and valence states are found comparable with typical photovoltaic materials (Si and CdTe). We have obtained a high open-circuit voltage of 1.75 V, fill-factor of 0.92 with maximum efficiency of about 23% under one sun condition with a thickness of 10 nm which suggests that SrSnBi2 stands as a potential candidate for photovoltaics. The calculated band-edges concerning normalizing hydrogen electrode appeal their use as efficient photo-electrocatalyst for water splitting. Overall, we suggest that the natural intermediate band gap-materials are promising candidate for low-cost and efficient photovoltaic and photo-electrocatalytic applications.