Investigation of Novel n-Doped a-Si/CZTSe Ultrathin-Film Solar Cell for Enhanced Performance

The ultrathin-film solar cell (UTFSC) technology has recently intrigued researchers with various chalcogenide materials, namely, copper indium gallium selenide (CIGS), copper zinc tin sulfide (CZTS), and copper zinc tin selenide (CZTSe), which exhibit formidable performance. The implementation of CZTSe as a second-generation thin-film absorber layer (due to its incredible light-absorbing capability) has motivated to design a UTFSC based on the CZTSe absorber layer. This work analyzed the possibility of a UTFSC by proposing a single-layer amorphous silicon (a-Si)/CZTSe structure (2-D). Due to its natural p-type characteristics, a-Si/CZTSe builds a p-n junction depletion layer that separates electron-hole pairs. Implementing different electric and optical parameters, and physical models, the efficiency of the solar cell is observed at different thicknesses. The optimized efficiency of the proposed structure is found to be 10.99%, at 700-nm CZTSe and 50-nm a-Si thickness. Also, an analysis is done after introducing defects in the CZTSe layer, which decreases the performance of the cell by around 0.4% (10.58%). At this optimized condition, the short-circuit current density (J_SC ), open-circuit voltage (V_OC), and fill factor (FF) are found to be 41.88 mA/cm², 0.548 V, and 46.05%, respectively. These results implicate a greater opportunity for the development of UTFSC in the near future involving nontoxic materials and a simple fabrication process.