Numerical analysis of BSF and ETL configurations for optimizing high-performance WSe 2 /MoTe 2 tandem solar cells

Abstract Tandem Solar Cells (TSCs) offer a strategic approach to surpass the efficiency limits of single-junction solar cells by harnessing complementary spectral absorption. This study explores the design and optimization of a novel TSC architecture composed entirely of Transition Metal Dichalcogenide (TMDC) materials, employing a WSe 2 -based top cell and a MoTe 2 -based bottom cell. The top cell leverages the tunable bandgap and superior carrier transport properties of WSe 2 to effectively harvest high-energy photons, while the MoTe 2 bottom cell is optimized to absorb lower-energy photons, enabling broad-spectrum solar utilization. The top cell architecture consists of an ITO/ETL/WSe 2 /HTL configuration, in which three (3) different electron transport layers (ETLs) and four (4) hole transport layers (HTLs) are evaluated to identify the optimal photovoltaic configuration. Key performance-affecting parameters including absorber thickness, doping density, defect density, and metal work function are systematically optimized. Following comprehensive optimization, the top cell with the configuration Al/ITO/ZnO/WSe 2 /CGSe/Ni achieves the highest performance, with a power conversion efficiency (PCE) of 33.50% . The pre-developed MoTe 2 -based bottom cell is tailored for tandem integration using a current-matching technique to align it’s short circuit current density (J sc ) with that of the top cell. The resulting WSe 2 /MoTe 2 tandem device demonstrates a power conversion efficiency of 58.73%, with a V OC of 2.28 V, a J SC of 32.86 mA cm −2 , and an FF of 78.4 % , outperforming the individual sub-cells. These theoretical results highlight the promising potential of all-TMDC tandem configurations for next-generation photovoltaic technologies.