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 Jsc 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 Jsc 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.