Exploring the correlation between the bandgap engineering and defect density toward high CTS solar cell efficiency

Ternary chalcogenide Cu2SnS3 (CTS) has emerged as a relevant compound for solar energy harvesting owing to its favorable optoelectronic properties. The aim of this study was to conduct a numerical investigation using SCAPS-1D software to determine the optimal conditions for an efficient CTS solar cell. The research focused on how the bandgap (Eg) design affects the optical properties and photovoltaic performance (PV) of a CTS solar cell. The correlation between the Eg width and bulk defect density (Nt), as well as the CTS/CdS interface defect density (Nit) of CTS thin films, was also investigated. The results revealed that the increase in Eg significantly improves the external quantum efficiency (EQE), power conversion efficiency (PCE), and open-circuit voltage (Voc) of the solar cells. In addition, a remarkable decrease in recombination rate was observed. For Eg values of 1.1 eV and 1.18 eV, the solar cell demonstrated a minimal recombination rate of 5 x 1020 cm-3 and a high PCE of 5%. The contour plot of Nt as a function of Eg confirmed that Eg and Nt values of 1.18 eV and 5 x 1016 cm-3, respectively, provide higher efficiency. Furthermore, the results highlighted the importance of limiting Nit to below 5 x 1014 cm-3 at the CTS/CdS junction. Under optimum conditions, the output parameters of the CTS solar cell were calculated to be 6.30% for the PCE, 46.64% for the fill factor (FF), 33.89 mA/cm2 for the shortcircuit current (Jsc), and 398.2 mV for Voc.