GeS monolayer as an emerging 2D semiconductor for heterojunction solar cells: A first principles and device-level study

Abstract

Two dimensional materials have emerged as a promising new class of photovoltaic materials due to their unique optoelectronic properties and tunable structures, offering new strategies to improve solar cell performance. Here, we employed periodic density functional theory (DFT) and SCAPS 1D simulations to investigate the photovoltaic potential of GeS. At the HSE06 level of theory, the unstrained GeS monolayer exhibits a E_g of 2.36 eV. Optical characterization confirmed the material’s intrinsic anisotropy, while strain-induced structural changes and enthalpy variations were also quantified. In the a-lattice direction, tensile strain increased the band gap from 2.42 to 2.60 eV, whereas compressive strain from −1 % to −5 % reduced it from 2.25 to 2.00 eV. Similar trends were observed in the b and ab directions. SCAPS 1D simulations reveal a power conversion efficiency (PCE) of 6.70 %, demonstrating the feasibility of GeS for photovoltaic applications. Additionally, impedance spectroscopy analysis was further used to investigate the charge transfer dynamics and resistive behavior in heterojunction solar cells with varying GeS layer thicknesses. These findings underscore the potential of GeS as a promising 2D semiconductor for the next generation solar cells and provide a comprehensive theoretical and computational framework for optimizing its integration into silicon-based heterojunction devices.