Antimony sulfide (Sb2S3) and thin crystalline silicon (c-Si) are considered suitable top- and bottom-cell candidates
for tandem solar cells (TSCs), owing to their natural abundance, non-toxicity, cost-competitiveness, and
complementary bandgaps. The current work proposes and investigates a two-terminal (2T) monolithic Sb2S3/Si
thin film TSC via TCAD simulation. The Sb2S3 cell, with a bandgap of 1.7 eV, is utilized as a top sub-cell, and the
bottom sub-cell is utilized by a thin c-Si cell having a bandgap of 1.12 eV. The calibrated standalone top and
bottom cells provide a power conversion efficiency (η) of 4.31% and 14.26%, respectively. Upon incorporating
the two cells into a 2T Sb2S3/Si monolithic TSC, the resultant tandem cell achieves an η of 10.10% implying that
the top cell should be optimized in order to get a tandem efficiency higher than the bottom cell. Thus, the Sb2S3
cell is optimized by designing the cell without the organic hole transport layer (HTL) (resulting in an np heterojunction)
and engineering the conduction band offset (CBO) between the electron transport layer (ETL) and
the Sb2S3 absorber. Then, the tandem structure is optimized starting from the ETL thickness and doping concentration.
Also, the impact of changing the absorber defect density and the series resistance of the top cell on the
TSC performance is investigated to demonstrate the maximum available η. At reduced defect density and series
resistance, the overall efficiency of the tandem cell is improved to 19.51%. Furthermore, we explored the impact
of top and bottom absorber thicknesses on TSC working metrics. At the designed matching point, the tandem
efficiency is enhanced to 23.25%, and Jsc also boosts to 17.24 mA/cm2. The simulation study is intended to
provide a tandem configuration that is based on an all-thin-film design which may be suitable for applications
like wearable electronics due to its flexibility. All TCAD simulations are performed using the Silvaco Atlas
simulator under standard one Sun (AM1.5G, 1000 W/m2) illumination. |
