Effect of electrodepositing and annealing parameters on properties of device-quality CuIn(Se,S)2 thin films on a Mo/glass substrate

Abstract

Device-quality CuInSe2-xSx thin films were prepared on Mo-coated glass substrates by one-pot electrodeposition and post annealing. CuInSe2 films were formed by simultaneous electrodeposition of Cu, In and Se in precursor chloride solutions with sulfamic acid and potassium biphthalate as complexing agents. The structure, morphology, and composition of CuInSe2 films could be controlled by deposition parameters, such as the composition of metallic precursors, the concentration of complexing agents, and the deposition potential and time. Dense and uniform In-rich CuInSe2 films of 1.5~2.0 μm thickness were successfully obtained in a narrow range of parametric variation of electrodeposition with a constant voltage of -0.5V vs. Ag/AgCl. The CuInSe2 films were annealed at high temperature ranging from 450℃ to 600℃ to produce further dense large-grain CuInSe2-xSx. The structure and morphology changed according to the atmosphere of Se/Ar (selenization) and H2S/Ar (sulfurization), concentration or flow rate of gases, annealing temperature and time, and temperature increasing and decreasing rates. Chemical etching of the annealed film with KCN solution also induced morphological and compositional change, producing a flat smooth In-rich CuInSe2-xSx film with less secondary phases, even though the etching condition was limited in a narrow range. The structure, morphology and composition of as-deposited CuInSe2 films and those of annealed CuInSe2-xSx films with and without KCN etching were compared with respect to the conditions of electrodeposition, annealing, and KCN etching using XRD, SEM, and EDS. In addition, electrical and photoelectochemical properties of well-prepared CuInSe2-xSx films were examined, and the proper condition for preparing device-quality CuInSe2-xSx films was proposed.