Interface and band engineering of CuTlS2 chalcopyrite solar cells using SnS2/NiO transport layers for enhanced photovoltaic performance

This work presents an in-depth numerical analysis of a CuTlS 2 -based heterojunction solar cell using SnS 2 and NiO as the electron and hole transport layers, respectively, with SCAPS-1D to model the properties. A systematic optimization of absorber thickness, doping concentration, defect density, work function of contact, and resistive losses shows an extremely interdependent relationship among optical absorption, band alignment, and recombination dynamics. For optimum parametric values, with an absorber layer thickness of 460 nm and a defect density of 1×10 14 cm -3 , the device demonstrated a power conversion efficiency (PCE) of 32.98%, an open-circuit voltage (V OC ) = 1.03 V, a short-circuit current density (J SC ) = 36.43 mA/cm 2 , and a fill factor (FF) = 87.21%. The spectral response analysis demonstrates a high External Quantum Efficiency (EQE) of ~85% across the visible spectrum. At the same time, recombination profiling confirms strong suppression of the bulk Shockley Read Hall (SRH) losses. Parametric studies further show that absorber defect density and back-contact energetics dominate voltage losses, whereas absorber thickness primarily governs photocurrent generation. These results establish CuTlS 2 as a defect-tolerant and electronically favorable absorber and identify transport-layer and contact engineering as decisive levers for performance enhancement. This work provides a quantitative design framework for high-efficiency CuTlS 2 -based thin-film solar cells and their potential as a competitive opportunity to conventional chalcopyrite absorbers.