Environmental benign and stable kesterite Cu2ZnSnS4 (CZTS) photovoltaics provides an intriguing alternative to conventional solar cells. However, further development is required for boosting the Voc-deficit in CZTS photovoltaic to enhance the cell function. Intending to obtain high-quality CZTS powder as the basis, here we report a comprehensive study of the vacuum annealing process (including annealing temperature, duration, and heating rates) for synthesized powder with the ball-milling method, which leads to a high-quality kesterite structure. According to analysis outcomes, there are not any significant differences in structures of differently milled specimens while the optical and morphological findings exhibit distinctive results. In short, the 10 h milled powder annealed at 500 °C for 5 h with a 9 °C min−1 heating rate possesses a high-quality structure alongside the desired 1.53 eV bandgap and optimum morphological characteristics.

Despite the potential as a promising alternative to CdTe and Cu(In,Ga)Se2, the kesterite compound Cu2ZnSn(S,Se)4 (CZTSSe) presents a critical challenge mainly from its high open-circuit voltage (Voc) deficit. Indeed, the Voc of the record CZTSSe solar cell to date has accounted for only 61% of that calculated by the Shockley–Queisser limit, whose origin can be ascribed to nonradiative recombination from a high density of defects and secondary phases. Therefore, an atomistic understanding and characterization of CZTSSe is highly essential to overcoming the current shortcomings in kesterite. This review discusses the advanced characterization techniques for studying the intrinsic properties of kesterite at a nanometer scale. Moreover, a cation substitution with an ionic mismatch around constituents is recognized as an effective route to address the fundamental limit (i.e., the cationic disorder) in CZTSSe. Here, we review recent studies on a novel chalcogenide Cu2BaSn(S,Se)4 that substitutes Zn with Ba and results in less cationic disordering.