Facile solution deposition of ZnIn2S4 nanosheet films on FTO substrates for photoelectric application

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 mm 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)).