A critical review of solution-process engineering for kesterite thin-film solar cells: current strategies and prospects

Abstract

The Cu₂ZnSn(S,Se)₄ (CZTSSe) material is considered a promising semiconductor material for commercial photovoltaic applications due to its high theoretical efficiency, high absorption coefficient, tunable direct bandgap, high element abundance, and low production cost. However, the efficiency of solution-processed CZTSSe thin-film solar cells still falls short of their theoretical efficiency limit (∼31.0%) and that of their predecessor copper indium gallium selenide (CIGS) cells. The relatively low device efficiency is mainly due to bulk and interface defects generated during the preparation of the absorber layer. For achieving a high-quality CZTSSe absorber layer via solution processing, the properties of the solvent are essential. To further improve the efficiency of CZTSSe cells prepared by solution methods, this review provides a detailed summary of the current research status on the selection of solvents and solutes or precursor materials, regulation of bulk and interface defects, optimization of various functional layers, and design of device structures in the preparation of high-efficiency CZTSSe by six solution methods based on different solvent systems (hydrazine, 1,2-ethylenediamine and 1,2-ethanedithiol, dimethyl sulfoxide, N,N-dimethylformamide, 2-methoxyethanol, and thioglycolic acid–ammonia systems). Finally, this article discusses new insights and perspectives for achieving high-efficiency CZTSSe thin-film solar cells.