A Critical Review on the Progress of Kesterite Solar Cells: Current Strategies and Insights

Kesterite Cu2ZnSn(S,Se)(4) (CZTSSe) with earth-abundant and environmental-benign constituents has been regarded as a promising solar energy harvesting material for green and cost-effective photovoltaic applications. The record efficiency of CZTSSe solar cells has recently been refreshed twice after years-long stagnation, keeping it in the spotlight. Nevertheless, the champion efficiency of 13.6% is still far behind its counterpart Cu(In,Ga)Se-2 (CIGS) (23.35%) despite being endowed with a similar electronic structure and nearly-identical device architecture. In fact, CZTSSe solar cells are more susceptible to non-radiative recombination at bulk and interfaces, which must be improved for further efficiency advancement. In this review, the state-of-art strategies to enhance the power conversion efficiency of CZTSSe solar cells are summarized and discussed, with focus given to three critical device regions i) kesterite absorber, ii) buffer/kesterite interface, and iii) kesterite/back contact interface. With the further elucidation of the latest progress and disclosure of fundamental mechanisms, novel insights toward high-efficiency kesterite solar cells are proposed.