Deposition and Characterization of Cu2ZnSnS4, Cu2CoSnS4 and Cu2NiSnS4 Thin films using Chemical Bath Deposition for Device Applications
Abstract
Background: Sustainable energy generation and conversions kestrite (Cu2ZnSnS4, Cu2CoSnS4 and Cu2NiSnS4) thin films solar cells are at the forefront of photovoltaic research interests, and devices based on the mineral kestrites could be the dark horse of next generation solar energy conversion. Hence, this work seeks to improve their efficiency. Methodology:The kesterites of Cu2ZnSnS4, Cu2NiSnS4 and Cu2CoSnS4, thin films were prepared on glass substrates using CBD. Result: Absorbance of the thin films varied from 0.3 to 0.7, the entire UV-VIS-NIR regions showing high absorbance at a wavelength of 200nm, and decreasing exponentially to 400nm, and gradually increased as wavelength increased. Transmittance varied as follows: Cu2CoSnS4 (02%),Cu2NiSnS4 (0-2.3%), and Cu2ZnSnS4 (0-2.2%) , the bandgaps of the films showing asfollows::Co2+ (1.20 eV- 1.30 eV) , Ni (1.25 eV–1.30 eV) and Zn2+(1.25eV -1.35eV) respectively, Zn2+ showing slight increase in the bandgap energies when compared to Co and Ni ion concentrations.Scanning electron micrographs showed a close packed morphology for all the samples, and a decrease in grain size, with doping ions of Co2+, Ni2+ and Zn2+ clearly seen in the micrographs for sample doped with Zn. Surface morphological study of Cu2CoSnS4, Cu2NiSnS4 and Cu2ZnSnS4 at (0.1M , 0.3M and 0.5M doping concentrations), showed that the grain size of all the samples were large and more oriented when doped with 0.5M and 0.3M concentration, compared to that with 0.1M. Conclusion : Synthesis and subsequent characterization revealed that dopants such as Co³⁺, Ni⁺, and Zn²⁺, with temperature treatment, enhanced the optical and structural properties of thin films.