Positive Role of Inhibiting CZTSSe Decomposition on Intrinsic Defects and Interface Recombination of 12.03% Efficient Kesterite Solar Cells

Cu 2 ZnSn(S,Se) 4 (CZTSSe) solar cells, which are emerging as promising photovoltaic devices, are currently suffering serious issues of large open‐circuit voltage deficit and low fill factor. Decomposition of CZTSSe is one of many factors limiting the efficiency improvement of CZTSSe solar cells, which can lead to the deviation of the chemical environment during the synthesis of CZTSSe. Herein, the Sn‐vapor is provided during the synthesis of CZTSSe to inhibit the decomposition, and the effect of decomposition on the intrinsic defects and interface recombination are systematically investigated. The high‐quality CZTSSe without the secondary phase and with the low Zn Sn and Cu Zn acceptor defects density is obtained. By inhibiting the decomposition, the recombination activation energy at depletion region is improved and the interface defect density is dramatically decreased, indicating the interface recombination is effectively reduced. Consequently, the performance of CZTSSe thin film solar cells, especially the open‐circuit voltage and fill factor, has been significantly improved. Finally, based on the excellent CZTSSe film, a photovoltaic device with 12.03% efficiency (active area efficiency is 12.96%) is prepared. These encouraging results provide a new route to controlling the defects and interface recombination of CZTSSe solar cells.