Characterization and understanding of performance losses in a highly efficient solution-processed CZTSSe thin-film solar cell

We present results on the characterization of a highly efficient CZTSSe solar cell fabricated using a solution-based process, aiming to gain a better understanding of its efficiency-limiting causes. Under red light illumination, we observed a red-kink in the current-density versus voltage (J-V) curve, likely due to a persistent photoconductivity in the buffer layer. Temperature-dependent J-V analysis suggests that interface recombination is the dominant loss mechanism. Defect analysis using admittance spectroscopy (AS) shows a single bulk defect level at ~63 meV and may be attributed to copper vacancy (V_Cu). The carrier concentration of the device determined using drive-level capacitance profiling (DLCP) is ~2.5×10¹⁶ cm^-3.