Enhanced performance of Sb₂Se₃-based solar cells with Fe doped CuGa(S,Te)2 as a secondary absorber

This study proposes a dual-absorber ₂ ₃ Sb ₂ Se ₃ -based solar cell incorporating Fe-doped C u G a ( S , T e ) 2 (Fe-CGST) as a secondary absorber layer. A systematic thickness optimization of both absorber layers is performed, identifying 2.6 μ m for ₂ ₃ Sb ₂ Se ₃ and 400 nm for Fe-CGST as optimal values. The introduction of an intermediate band (IB) through Fe doping enables sub-bandgap photon absorption, enhancing carrier generation and spectral utilization. The optimized device demonstrates significant improvements in key photovoltaic parameters, including open-circuit voltage ( V oc ), short-circuit current density ( J sc ), fill factor (FF), and overall efficiency ( η ). A maximum efficiency of 18.54% is achieved, compared to 10 . 12% for the conventional structure. Detailed optoelectronic analysis, including EQE, capacitance–voltage (C-V), and Nyquist characteristics, reveals improved charge transport, reduced recombination losses, and enhanced carrier collection efficiency. These findings highlight the effectiveness of combining dual-absorber design with intermediate band engineering for high-performance thin-film solar cells.