Design and analysis of Sb2S3/Si thin film tandem solar cell

Abstract

Antimony sulfide (Sb2S3) and thin crystalline silicon (c-Si) are considered suitable top- and bottom-cell candi- dates 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 het- erojunction) 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 con- centration. 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.