The Influence of Removal of Secondary Phases and Dissolution By-Product from the Surface of Cu 2 ZnSnS 4 Film on the Photoelectrochemical Response of This Film

Abstract

© 2020 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited. The influence of surface treatment of as-synthesized Cu2ZnSnS4 (CZTS) thin films on the photocurrent response in the photoelectrochemical cell with Eu3+ contact has been studied. With our work we are the first, to our knowledge, to show that in order to achieve the maximal photocurrent response of CZTS, dissolution of copper sulfide in a KCN solution and subsequent dissolution of ZnS in a HCl solution is insufficient. An additional treatment in a KCN solution for only 10 s can results in the highest photocurrent density. XPS, photoelectrochemical and the Mott-Schottky measurements reveal a negatively charged layer of surficial chlorides on the CZTS film. This layer was captured during removal of the ZnS secondary phase from CZTS film surface in a HCl solution. It has been shown that this layer is the reason why it was impossible to reach the maximum photocurrent. XRD, SEM and XPS measurements demonstrated the dissolution of copper sulfide in a KCN solution, zinc sulfide in a HCl solution and removal of a thin layer of copper chloride during a short (10 s) additional treatment in a KCN solution.