Facile solution deposition of ZnIn2S4nanosheet films on FTO substrates for photoelectric application

Abstract

In this paper, ZnIn₂S₄ perpendicular nanosheet films have been directly deposited on FTO substrates by a facile hydrothermal method and investigated as the electrode materials for solar cells. The crystal structure, morphology, and optical properties of the obtained ZnIn₂S₄ films were characterized by measurements such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive spectrum (EDS), X-ray photoelectron spectrum (XPS) and UV-vis spectra. The results revealed a uniform perpendicular ZnIn₂S₄ film with thickness of 4 μm and with an average nanosheet thickness of about 30 nm on FTO substrate, along with the band gap of 2.35 eV. The reaction conditions influencing the formation of ZnIn₂S₄ films, such as the substrate treatment and reaction time were investigated. A possible mechanism for the formation of ZnIn₂S₄ films on FTO substrates under hydrothermal conditions has been proposed. Furthermore, after heat treatment, the ZnIn₂S₄ film electrode exhibited a photoelectrical conversion efficiency of 0.23% in FTO/ZnIn₂S₄/polysulfide/Au liquid-junction solar cell under AM 1.5 (100 mW cm⁻²).