Investigation on highly flexible CZTS solar cells using transparent conductive ZnO/Cu/ZnO films

Transparent conductivity oxide (TCO) films played an essential part in flexible CZTS solar cells (CSCs), which required excellent transparent conductivity and flexibility of TCO films. The inferior flexibility of ITO films, a commonly used material in TCO films, limited the development of flexible CSCs. In this paper, the ZnO/Cu/ZnO (ZCZ) TCO film with high transmittance and flexibility was prepared by radio frequency magnetron sputtering and applied as a transparent conductive layer for flexible CSCs to improve the flexibility of CSCs. The CSCs with ZnO/Cu(9 nm)/ZnO (ZC9Z) film exhibited a power conversion efficiency (PCE) of 6.01% without bending, higher than that of CSCs with ITO film. The PCE ratio of CSCs with ZC9Z film to that of CSCs with ITO film was 5.83 and 9.09 after a bending diameter of 8 mm and 1000 cyclic bending, showing that CSCs with ZC9Z film were of excellent flexibility. [Display omitted] •ZCZ films on PET substrates exhibit high bending tolerance than ITO films.•ZCZ films' average transmittance and resistivity are 80.9% and 4.03 × 10−4 Ω·cm.•ZCZ films present excellent long-cycle stability.•ZC9Z CSCs present a PCE of 6.01%, which is almost 2% higher than that of ITO CSCs.