Effects of Bi and S co-doping on the enhanced photoelectric performance of ZnO: Theoretical and experimental investigations

Abstract

The enhanced photoelectric performance of (Bi, S) co-doping ZnO is explored by combining the density functional theory (DFT) calculations with experimental measurements. The crystal structures, formation energies, electronic properties and relative effective mass of photogenerated electrons and holes of pure and (Bi, S) co-doped ZnO are investigated by DFT calculations. Results indicate that Bi/S co-doping can generate impurity states and shift the conduction band into the lower energy region, causing the decrease in band gap. Relative effective mass show that the separation rates of photogenerated carriers are enhanced after modification. Moreover, experimental measurements are carried out on the basis of the above theoretical analysis. Pure and Bi/S co-doped ZnO samples with different doping ratios are synthesized and characterized. The results confirm that the presence of (Bi, S) has major effects on oxygen defects in crystal structure. XPS, UV–vis and PL studies evidence the roles of these oxygen defects on band gap narrowing for 2% ZnO samples. As expected, 2% doping sample has the highest photocurrent value (23.58 μA cm−2, nearly 4.7 times higher than pure ZnO) and the smallest Nyquist semicircle diameter. This work will provide some new insights into the design of high performance photoelectrocatalysis materials.