Unravelling the intricacies of selenization in sequentially evaporated Cu(In,Ga)Se2 Thin film solar cells on flexible substrates

Abstract

Abstract This study aimed to fabricate copper indium gallium diselenide (CIGSe) thin films using a novel two-step approach. Firstly, we deposited metallic precursors (Cu/In/Ga) onto a Mo-coated stainless steel substrate using thermal evaporation at unintentional substrate temperature. Subsequently, selenization was carried out in a furnace under the presence of an inert gas. The quality of the CIGSe thin films was analyzed to explore the influence of selenization temperature (450 °C–550 °C) and duration (30 and 60 min), while maintaining an inert atmosphere inside the selenization furnace. The structural analysis revealed the progressive development of additional phases over time, resulting in the formation of a complete chalcopyrite CIGSe structure with the preferred reflection on the (112) plane. The absorber layer exhibited a thickness of 2 μm, with atomic ratios of 0.83 for Cu/(In+Ga) and 0.24 for Ga/(In+Ga) in the film selenized at 550 °C. P-type conductivity was observed in the CIGSe thin film, with a carrier concentration of up to 1017 cm−3, and it displayed a well-defined and uniform morphology characterized by a large grain size of approximately 0.9 μm. Utilizing the optimized conditions, we successfully fabricated solar cells on a flexible substrate, achieving a photoconversion efficiency of up to 9.91%. This research delves into the impact of selenization parameters on the growth of CIGSe absorber layers and introduces a new approach that could significantly influence the feasibility and industrialization of flexible solar cells.