First-principles investigation on the impact of copper concentration on zinc telluride as the back contact for cadmium telluride solar cells

• Main Authors: Ahmad N.I., Doroody C., Norizan M.N., Ahmad M.F., Rahman K.S., Radzwan A., ALOthman Z.A., Katubi K.M., Alzahrani F.M., Amin N., Kar Y.B.
• Other Authors: 57200991933
• Format: Article
• Published: Springer Science and Business Media Deutschland GmbH 2025
• Subjects: Cadmium telluride; Copper compounds; Energy gap; II-VI semiconductors; Schottky barrier diodes; Semiconductor doping; Thin film solar cells; Thin films; Zinc compounds; Back contact; Back surface field; Backsurface field; Cadmium telluride solar cells; Density functional theory; Density-functional-theory; Energy; Thin-films; Zinc tellurides

Cadmium telluride (CdTe) solar cells have attracted a lot of interest in recent years, attributed to their low cost and eco-friendly fabrication technique. However, the back contact is still the key issue for further improvement in device performance due to the work function difference between p-CdTe and metal contacts. In this study, the interatomic characteristics of zinc telluride (ZnTe) and Cu-doped ZnTe (ZnTe:Cu) as a back surface field (BSF) in CdTe structure is investigated using first-principles density functional theory (DFT) to overcome the Schottky barrier in CdTe solar cells. The incorporation of different doping levels of copper (Cu) in ZnTe on an atomic scale, where Zn1?xTe:Cux (x = 0, 2, 4, 6, 8, and 10) as the potential back surface field layers is investigated. The effect of doping concentration on electrical characteristics such as bandgap structure and density of states (DOS) were examined via ab initio with the Hubbard U (DFT + U) correction. The results showed an interesting gradual decrease in the bandgap energy of ZnTe from 2.24�eV to 2.10�eV, 1.98�eV, 1.92�eV, 1.88�eV, and 1.87�eV for the incremented value of Cu content of 3.13%, 6.25%, 9.38%, 12.50%, and 15.63%, respectively. Accordingly, it has been found that controlling of the effective copper doping, i.e., concentration, is crucial for developing efficient back contact junctions for high-efficiency CdTe thin-film solar cells. ? 2024, The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.