Fabrication of Cu2ZnSnS4 thin films on flexible polyimide substrates by sputtering and post-sulfurization

Abstract

Flexible Cu2ZnSnS4 (CZTS) thin films are more advantageous than those on rigid glass substrates. In this study, vacuum-based magnetron sputtering was utilized to fabricate CZTS thin films on flexible polyimide substrates. Zn/Sn/Cu precursors were sputtered and then sulfurized. The influences of sulfurization temperature on the structural, compositional, morphological, electrical, and optical properties of the fabricated thin films were analyzed. The experimental results show that the CZTS structures form on the polyimide substrates after sulfurization. The crystallinity of CZTS enhances and the secondary phases in the thin films decrease with increasing sulfurization temperature. Single-phase CZTS thin films are obtained for sulfurization temperatures reaching 450 °C. The compositions of the fabricated thin films are Cu-poor and Zn-rich. The fabricated CZTS thin films show p-type conductivity. The direct optical band gaps of the thin films range from 1.51 eV to 1.55 eV. The absorption coefficients of these films are larger than 1 × 104 cm−1 above the band gap edge. The experimental results reveal the feasibility of the deposition of CZTS thin films on polyimide substrates by vacuum-based methods. The fabricated thin films can suitably function as absorbers for solar cell applications.