Kesterite compound semiconductors for thin film solar cells

Thin film solar cells based on Cu2ZnSn(S,Se)4, “CZTS”, are attractive by combining high light absorption and high abundance of constituent elements. The efficiency of CZTS solar cells developed rapidly during the last decades, but significant improvements are still needed to reach commercially viable levels. This review covers the most recent trends in CZTS research; (i) alloying with new elements, (ii) exchange of CdS buffer layer with alternative materials, (iii) back contact engineering and (iv) defect studies as a function of compositional variations and annealing. Better understanding of the material and device limitations is expected to emerge from this research. In the perspective of large scale use of CZTS modules, non-toxicity and earth-abundance cannot be compromised in the view of competition with commercially mature CdTe and CIGS technologies. Large band gap kesterite derivatives for stable top cells in tandem solar cells is an interesting and less explored field meriting more attention.