Numerical Simulation to Achieve High Efficiency in CuTlSe2–Based Photosensor and Solar Cell

This article presents the design and numerical investigation of a novel dual-function architecture that integrates a photosensor (PS) and a solar cell (SC), based on the chalcogenide compound copper thallium selenide (CuTlSe₂), utilizing cadmium sulfide (CdS) as the window layer and germanium sulfide (GeS) as the back surface field (BSF) layer. Simulations have been conducted using SCAPS-1D software, utilizing material parameters obtained from the literature and previously reported experimental studies. The optimized device, with the GeS BSF layer, achieves a power conversion efficiency (PCE) of 31%, an open-circuit voltage (V_OC) of 0.84 V, a short-circuit current density (J_SC) of 43.18 mA cm⁻², and a fill factor (FF) of 85.88%. In contrast, without the BSF layer, the device delivers a reduced PCE of 22.97%, J_SC of 38.64 mA cm⁻², V_OC of 0.73 V, and FF of 81%. Additionally, the proposed structure reveals superior photosensing performance, achieving a peak responsivity (R) of 0.78 A W⁻¹ and detectivity (D^∗) of 2 × 10¹⁵ Jones at a photon wavelength of 1040 nm in the presence of the BSF layer. The device exhibits enhanced spectral response in the near-infrared (NIR) region, specifically within the wavelength range of 800–1100 nm, emphasizing its proficiency in NIR light detection. These findings highlight the potential of CuTlSe₂–based structures for efficient dual-function photovoltaic (PV) and photosensing applications.