Computational analysis of AgXSe2 (X = Ga, Sb)-based 2 T tandem solar cell: A pathway to >39% efficiency

• Design and simulation of novel AgGaSe 2 /AgSbSe 2 2 T tandem via SCAPS-1D. • Optimized bandgap combination for efficient current matching. • Thickness tuning enables Jsc ≈ 23.43 mA·cm −2. • Achieves high Voc (1.93 V) with reduced recombination losses • High PCE of 39.88% achieved at current-matching condition. Tandem solar cells have emerged as an effective solution for surpassing the Shockley-Queisser (SQ) efficiency limits of single-junction systems by enabling more efficient utilization of the solar spectrum and achieving higher power conversion efficiencies. This article reveals a theoretical performance of novel AgXSe 2 (X = Ga, Sb)-based two terminal (2 T) tandem solar cell. The top absorber, AgGaSe 2 (1.65 eV), and the bottom absorber, AgSbSe 2 (1.00 eV), are strategically chosen to allow efficient spectral splitting and enhanced tandem performance. As well, the identical window and back surface field (BSF) layers are incorporated in both subcells to ensure a consistent and well-defined device architecture. The top subcell adopts the n-ZnSe/p-AgGaSe 2 /p + -Zn 3 P 2 structure, while the bottom subcell consists of an n-ZnSe/p-AgSbSe 2 /p + -Zn 3 P 2 configuration within the 2 T tandem device. SCAPS-1D simulation tool is used to analyze the proposed tandem architecture. A comprehensive parametric analysis is performed to evaluate the impacts of the thickness, carrier level, and bulk defects in each layer of both subcells on the proposed device. Current matching is achieved by setting the thickness to 1.23 µm of AgSbSe 2 under a filtered spectrum, thereby aligning the short circuit current density (J SC ) of the top and bottom subcells. The optimized AgXSe 2 (X = Ga, Sb)-based tandem solar cell attains a significant open circuit voltage (V OC ) of 1.93 V, a J SC of 23.43 mA·cm −2 , a fill factor (FF) of 88.18% and notable efficiency of 39.88% at the current matched condition. These results provide valuable insight for advancing the design of high-efficiency tandem solar cells.