An evaluation of depletion layer photoactivity in Cu2ZnSnS4 thin film

Cu2ZnSnS4 films were examined in Eu3+/Eu2+ electrolyte to evaluate various analytical expressions for photocurrent response as a function of applied potential. A Gärtner model, which considers charge transfer (across the double layer) was evaluated. This model shows an adequate fit in the negative photocurrent region. The fit of the Gärtner model over a broader range of photocurrent is improved by modifying it to include the contributions due to space charge current and dark current as proposed and demonstrated in this study. Various other models and relevant fitting parameters are also evaluated and discussed in this article. - Highlights: ► A photostimulated interfacial charge transfer process was investigated for CZTS. ► Consideration of dark current in the positive bias region improves fitting. ► Contribution of distributed electronic states in electrolyte for CZTS absorbers. ► Consideration of space charge recombination phenomenon improves fitting.