Modeling of highly efficient CNGS based kesterite solar cell: A DFT study along with SCAPS-1D analysis

The electronic and optical properties of Cu₂NiGeS₄ (CNGS) are examined using the first-principle DFT calculations. A unique mBJ + U potential method is used for the band gap energy calculation of CNGS. With a remarkably high absorption coefficient (10⁴ cm⁻¹), CNGS has become a promising candidate for photovoltaic applications. SCAPS-1D tool is used to simulate a thin-film solar cell with a Mo/MoS₂/Cu₂NiGeS₄ (CNGS)/CdS/ZnO/ZnO:Al structure. The impact of various factors, such as layer thickness, donor and acceptor concentrations, and defect density on the CNGS layer was explored. This study also explores the combination of suitable buffer layers (such as CdS, ZnS, and their alloy Cd_1−xZn_xS), along with different doping concentrations and thicknesses, to be used as suitable buffer layers in the CNGS solar cell. The simulation outcomes suggest that the optimal thickness for the absorption layer in CNGS solar cells is between 2000 and 2400 nm, while the ideal thickness for MoS₂ is 100 nm. The buffer layer should be between 20 and 50 nm. Keeping the defect density of CNGS below 10¹⁴ cm⁻³ is crucial for high efficiency. The optimized results yield an efficiency conversion rate of 20.05%, a 66.77% fill factor, a short-circuit current of 29.67 mA/cm² and an open-circuit voltage of 0.983 V.