A straightforward one-pot approach to two new defect energy levels in ZnS

In this study, for the first time, we report a straightforward one-pot method to obtain ZnS with multiple vacancies (V₊V₋–ZnS). It is found that two new defect energy levels are formed by Zn vacancies and S vacancies, which are close to the valence band (VB) top and conduction band (CB) bottom, respectively. The newly formed energy levels in V₊V₋–ZnS greatly enhance light absorption: 480 nm and 2.44 eV (V₊V₋–ZnS) vs. 399 nm and 3.24 eV (ZnS). Moreover, V₊V₋–ZnS exhibits an evidently improved charge separation efficiency. Thus, V₊V₋–ZnS shows a high visible-light activity, while ZnS has no response to visible light. This method is simple, and could be extended to mass production.