Achieving over 10% device efficiency in Cu2ZnSn(S,Se)4 thin-film solar cells with modifications of window layer properties

Zinc oxide (ZnO) is a widely studied transparent conducting oxide material because of its tunable optical and electrical properties. Herein, the optical, electrical, and structural properties of ZnO thin films co-doped with metal atoms and fluorine (F) are investigated. The ZnO thin films are co-doped with Al, Ga (2.0 wt%), and F (0.5 wt%) and deposited using radiofrequency magnetron sputtering. In a comparative study of F doping, the thin films doped with F exhibited improved optoelectronic and structural properties compared to the undoped thin films. The thin films co-doped with metal and F exhibited a surface passivation effect, which decreased their resistivity and increased their transmittance in the long-wavelength region. The ZnO thin films co-doped with F exhibited the best resistivity, mobility, and transmittance values of 4.27 Ω·cm, 24.1 cm2/V·s, and 91.17%, respectively. Finally, when these thin films were applied to CZTSSe thin-film solar cells, the short-circuit density and fill factor of the cells increased, while their series resistance decreased. Consequently, the power conversion efficiency of the cells increased to 10.12% when the FGZO layer was used. [Display omitted] •Fluorine doping had a passivating effect on ZnO thin films.•Improving the characteristics of the window layer improved solar cell performance.•FGZO (F and Ga co-doped ZnO) applied CZTSSe solar cell showed the best efficiency of 10.12%.