Tuning the band gap of hematite α-Fe2O3 by sulfur doping

Based on the density functional theory, the band structure and optical absorption of the isovalent sulfur-doped hematite α-Fe2O3 are studied systematically. The results show that the band gap of α-Fe2O3 − xSx decreases monotonically with increasing the sulfur concentration, resulting in an obvious increase of the optical absorption edge in the visible range. Most intriguingly, unlike the pure α-Fe2O3 material, the α-Fe2O3−xSx with x≈0.17 (S concentration of ∼5.6%) exhibits a direct band gap of an ideal value (∼1.45 eV), together with high optical absorption (∼105 cm−1) and lower carriers effective masses. These results indicate that α-Fe2O3 − xSx, with a proper concentration of sulfur, may serve as a promising candidate for low-cost solar-cell materials.