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 alpha-Fe2O3 are studied systematically. The results show that the band gap of alpha-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 alpha-Fe2O3 material, the alpha-Fe2O3-xSx with x approximate to 0.17 (S concentration of similar to 5.6%) exhibits a direct band gap of an ideal value (similar to 1.45 eV), together with high optical absorption (similar to 10(5) cm(-1)) and lower carriers effective masses. These results indicate that alpha-Fe2O3-xSx, with a proper concentration of sulfur, may serve as a promising candidate for low-cost solar-cell materials. (C) 2013 Elsevier B.V. All rights reserved.