Simulation analysis of functional MoSe2 layer for ultra-thin Cu(In,Ga)Se2 solar cells architecture

The influence of Molybdenum diselenide transition metal dichalcogenide material (p-type MoSe2 TMDC) as an interfacial layer between the ultra-thin Cu(In,Ga)Se-2 (GIGS) absorber layer, with thickness less than 500 nm, and molybdenum back contact was studied using SCAPS-1D simulation package. The possible effects of the p-MoSe2 layer on the electrical properties and the photovoltaic parameters of the CIGS thin-film solar cells have been investigated. Band gap energy, carrier concentration, and the layer thickness of the p-MoSe2 were varied in this study. The optimum band gap is found to be of 1.3 eV. Interfacial layers of thicknesses less than 200 nm have been found to cause deterioration for the overall cell performance. This might be attributed to the increase in the back-contact recombination current and the reduction of the built-in potential at p-MoSe2/CIGS junction. Furthermore, the MoSe2 layer would form the so-called back surface field (BSF), due to the associated wider band gap with respect to that of CIGS absorber layer. Additionally, the simulation of the I-V characteristic showed a higher slope which implies that MoSe2 layer at the CIGS/Mo interface acts in a beneficial way on the CIGS/Mo hetero-contact adapting it from Schottky type contact to quasi-ohmic contact. The conversion efficiency has increased significantly from 14.61% to 22.08%, without and with the MoSe2 layer, respectively. These findings are very promising for future high performance and cost-effective solar cell devices.