Sol–Gel Dip-Coated Cu2ZnSnS4 Thin Films as High-Performance Absorber Layers for Solar Cells: Experimental Investigations Combined with DFT Simulations

Abstract

In this study, Cu₂ZnSnS₄ (CZTS) thin films with a kesterite-type structure were successfully deposited via a sol-gel dip-coating method using a chemically derived precursor solution. X-ray diffraction (XRD) analysis confirmed the formation of a single-phase kesterite structure with a dominant (112) orientation at 2θ = 28.57° and an average crystallite size of 17.78 nm. The experimentally determined lattice parameters (a = 5.42 Å, c = 10.75 Å, c/a = 1.98) are in close agreement with density functional theory (DFT) calculations using the full-potential linearized augmented plane wave (FP-LAPW) method, which yielded a = 5.36 Å, c = 10.74 Å, and c/a = 2.00. Optical characterization revealed a high absorption coefficient (~10⁴ cm^–1) and an optical band gap of 1.47 eV, indicating suitability for photovoltaic applications. Notably, the calculated band gap (1.48 eV) closely matches the experimental value, demonstrating strong quantitative agreement between theory and experiment. This combined experimental-theoretical approach highlights the potential of sol–gel dip-coated CZTS thin films as efficient absorber layers for low-cost, environmentally friendly solar cells.