A Comprehensive Review on the Recent Strategy of Cation Substitution in CZTS(Se) Thin Films to Achieve Highly Efficient Kesterite Solar Cells

Kesterite Cu 2 ZnSnS 4 (CZTS) and selenized CZTS (CZTSSe) are the most potential replacements of Cu(In x Ga 1− x )Se 2 as absorber layers in thin‐film solar cells, aligning with modern green energy policies. In spite of a reported power conversion efficiency ( η ) of nearly 14.9%, their efficiency still lags much behind their predecessors like cadmium telluride and CIGS. Major obstacles hindering the performance of CZTS‐based thin‐film solar cells pertain to the formation of Cu Zn and Zn Cu antisite defects, along with high density of 2Cu Zn + Sn Zn donor defects, which adversely affects open‐circuit voltage and η . To combat these challenges, researchers have explored cation substitution by incorporating alternative isovalent atoms, such as substituting Ag/Li for Cu, Mn/Cd for Zn, and Ge/Ti for Sn, as a potent strategy to inhibit severe potential fluctuations and undesirable tail states caused by Cu–Zn disorder and Sn‐related defects. Recently single‐cation substitution in CZTS (or CZTSSe) has garnered considerable attention, while dual‐cation incorporation has emerged as an intriguing avenue to enhance device performance, although in its nascent stage of research and development. This review discusses recent progress on cation substitution to suppress antisite defects in CZTS (or CZTSSe), leading to high‐efficiency thin‐film solar cells.