First principles prediction of the elastic, electronic and optical properties of Sn3X4 (X = P, As, Sb, Bi) compounds: Potential photovoltaic absorbers

We report a first-principles study of structural, mechanical and optoelectronic properties of the Sn3X4 (X = P, As, Sb, Bi) compounds. The calculations were performed using the full-potential linearized augmented plane wave approach (FP-LAPW). The structural and mechanical properties of Sn3X4 (X = P, As, Sb, Bi) compounds were obtained using GGA-PBE. In addition, The Tran-Blaha modified Becke-Johnson exchange potential (TB-mBJGGA) technique was used to calculated the optoelectronic properties. The calculated electronic band structures and density of states reveal a direct band gap at F points varied from 0.11 eV to 1.23 eV for X = P, As, Sb, Bi. The optical absorption calculations show that all compounds have high absorption coefficients about twenty times greater than that of CuInSe2 and CdTe in the visible region. The high absorption of these materials could be attributed to the localized p-states of cation (X = P, As, Sb, Bi) in the lower region of the conduction band.