Enhancement of CZTS photovoltaic device performance with silicon at back-contact: A study using SCAPS-1D

• CZTS PV devices were studied using SCAPS-1D with p+ type Si at back-contact. • a-Si:H eliminates downward band-bending at the back-contact thus improving J sc . • The η values are 16.83% and 21.85% with c-Si and a-Si:H, respectively. • η is further enhanced when CZTS is replaced by CZTSSe while Si being at the back-contact. Cu 2 ZnSnS 4 (CZTS) is a promising photo-absorber material for photovoltaics (PV) applications. Molybdenum which is employed as a back-contact metal in the CZTS based PV devices, is not the best choice. In the present work, we have used one-dimensional Solar Cell Capacitance Simulator (SCAPS-1D) to study the effect of replacing molybdenum with p+- type silicon (Si), both in the crystalline and hydrogenated amorphous phases. The device models with these two phases of Si at the back-contact led to photoconversion efficiencies ( η ) of 16.83 and 21.85%, respectively. Moreover, with Si at the back-contact, the performance can be further enhanced to 22.45% with the introduction of selenium in the chalcogenide sub-lattice. These improved η values are due to improved short-circuit current and fill-factors; the open-circuit voltage remains unchanged. The reduction of Schottky barrier at the back-contact with the use of Si is resulting in these beneficial effects.