Temperature‐Modulated Nucleation Engineering Enables Uniform Distribution of Cations for Efficient Kesterite Solar Cells

Abstract Kesterite Cu 2 ZnSn(S,Se) 4 (CZTSSe) has emerged as a highly promising photovoltaic material because of its environmentally friendly characteristics and low cost. However, as a multicomponent inorganic semiconductor material, the complex nature of CZTSSe leads to disorder in the crystallization reaction process at high‐temperature selenization, resulting in numerous antisite defects that cause significant non‐radiative recombination and open circuit voltage loss of the final photovoltaic device. Therefore, it is a great challenge to fabricate high‐quality CZTSSe absorbers with homogeneous chemical composition and uniform cation distribution for achieving high‐efficiency solar cells. Herein, synergistic crystallization and uniform cation distribution have been successfully realized via temperature‐modulated homogeneous nucleation strategy. This strategy effectively leads to more homogeneous nucleation sites with larger nuclei sizes for high‐quality CZTSSe thin films with uniform cation distribution. As a result, high‐efficiency CZTSSe solar cells over 14% have been realized. This work reveals the mechanism of uniform nucleation, providing a simple and feasible route for high‐quality CZTSSe thin films and high‐efficiency CZTSSe solar cells.