Solvothermal synthesis of nanostructured CuInS2 thin films on FTO substrates and their photoelectrochemical properties

This study reports the growth of CIS nanosheets and nanoworms on FTO glass through a surfactant-assisted solvothermal process. The as-prepared products are single crystalline in tetragonal structure with the crystal lattice spacing of about 0.32 nm which agrees with the (112) plane of CIS. The formation process is investigated and a possible growth model is proposed. Both oxalic acid and CTAB are found to play important roles during the formation process of the CIS thin films. Raman analysis reveals that the film quality can be simply adjusted by changing the ratio of the reactants and that higher content of TU will lead to better crystallinity. The direct band gap values of the CIS nanosheets and nanoworms are calculated to be 1.50 and 1.55 eV, respectively. Both values are very close to that of bulk CIS (1.53 eV). The PEC properties of the CIS nanosheets and nanoworms are studied as well. Compared with the nanosheet electrode, these nanoworms synthesized in sulfide-rich environment exhibit better photoelectric performance due to their better visible-light absorption and improved film conductivity.