Full optoelectronic simulation of all antimony chalcogenide thin film tandem solar cell: Design routes from 4-T to 2-T configuration

Antimony chalcogenide, as a newcomer to light harvesting materials, is regarded as an auspicious contender for incorporation as a photoactive layer in thin film tandem solar cells (TFTSCs). The current study introduces the design of all-antimony chalcogenide TFTSC comprised of an Sb₂S₃ (1.7 eV) front subcell and an Sb₂Se₃ (1.2 eV) rear subcell. The challenges to migrating from four-terminal (4-T) to two-terminal (2-T) designs are highlighted and possible solutions are proposed. To commence, a calibration procedure for the two subcells is conducted in alignment with experimental investigations. The benchmarked solar cells yield a power conversion efficiency (PCE) of 8.08 % for the upper subcell and 10.58 % for the lower subcell. Subsequently, upon integration of both subcells within the initial 4-T Sb₂S₃/Sb₂Se₃ TFTSC, the resultant PV cell attains a PCE of 12.27 %. Before transitioning it to a more efficient 2T tandem configuration, we explore alternative inorganic HTL materials to the Spiro-OMeTAD HTL to overcome its practical considerations. Cu₂O is found to be the best HTL alternative to be included for both subcells. Upon stacking into the tandem structure, the combined cell exhibited an efficiency of 15.68 % and a notable J_sc of 16.23 mA/cm². To further enhance the tandem performance, the device structure is optimized by engineering the CBO of two sub-cells and employing a double ETL design for the front sub-cell. At the considered current matching criterion, the tandem device PCE and J_sc are boosted to 27.86 % and 17.60 mA/cm², respectively. Based on this full optoelectronic analysis, developed in the Silvaco TCAD environment, a 2-T all antimony chalcogenide tandem configuration can be realized and optimized, paving the way for future experimental endeavors.