A comprehensive study on ZnSnN2-based solar cells with different Cu-based delafossite as buffer layers: A numerical analysis using SCAPS-1D

This study investigates four Cu-based Delafossite materials (i.e., CuGaO 2 , CuCrO 2 , CuAlO 2 , and CuFeO 2 ) as potential buffer layer candidates for ZnSnN 2 -based solar cells with the general configuration ITO/CuMO 2 (M = Ga, Cr, Al, and Fe)/ZnSnN 2 /Ag. We conducted the simulations using the SCAPS-1D software. Various physical parameters, including the thickness of each layer, carrier doping concentrations in different layers, and defect densities (both in the bulk region and at the interfaces), were investigated. Additionally, resistances, operating temperature, capacitance-voltage characteristics, and impedance spectroscopy were also examined. The ZnSnN 2 absorber layer thickness and Cu-based Delafossite layers thickness for all devices were optimized to 2 μm and 50 nm, respectively. Furthermore, the simulation results indicate that, for better performance, the doping concentrations in the ZnSnN 2 layer (N D ) and Cu-based Delafossite layers (N A ) were optimized to 1 × 10 19 and 1 × 10 20 cm −3 , respectively. The bulk defect density of the absorber layer and buffer materials is approximately 10 14 cm −3 , while the interface defect density at the ZnSnN 2 /CuMO 2 interface is approximately 10 15 cm −2 . Mott-Schottky analysis determined V bi values of 1.68 V, 1.74 V, 1.70 V, and 1.68 V for CuGaO 2 , CuCrO 2 , CuAlO 2 , and CuFeO 2 buffer layers, respectively. ZnSnN 2 -based solar cells with these buffer layers achieved power conversion efficiencies (PCE) of 21.637 %, 18.573 %, 21.630 %, and 18.535 %, respectively, under buffer-side illumination. Additionally, all devices exhibited a negative temperature coefficient ( C T ). The study suggests that using Cu-based Delafossite as buffer layers is a promising approach for manufacturing cost-effective and highly efficient ZnSnN 2 -based solar cells, due to their low cost, inherent p-type properties, and non-toxic nature.