Study on the Photoelectrochemical Properties of AgInS2 and Ga-doped AgInS2 Thin Films Prepared by Electrodeposition Method

• Main Authors: Chih-hao Wang, 汪志豪
• Other Authors: Chung-jen Tseng
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/68107703828543531428

博士 === 國立中央大學 === 機械工程研究所 === 100 === Silver-indium-disulfide (AgInS2) and Gallium-doped silver-indium-disulfide (Ga-doped AgInS2) thin films have been prepared on the fluorine-doped tin oxide (FTO) coated glass substrates using a one-step electrodeposition method. A new procedure for the deposition of AgInS2 and Ga-doped AgInS2 thin films is reported. The effect of the [Ag]/[In] molar ratio in solution bath on the structural, morphological, and photoelectrochemical properties of AgInS2 films was examined. X-ray diffraction patterns of films show that the films are the polycrystalline AgInS2 phase. The thicknesses, direct band gaps, and indirect band gaps of the films were in the ranges of 209 to 1021 nm, 1.82 eV to 1.85 eV, and 1.44 to 1.51 eV, respectively. The carrier densities and flat-band potentials of films obtained from Mott-Schottky and open-circuit potential measurements were in the ranges of 4.2×1019 cm-3 ~ 9.5 ×1019 cm-3 and -0.736 ~ -0.946 V vs. normal hydrogen electrode (NHE), respectively. It was found that the films with molar ratio of [Ag]/[In] = 0.8 in solution bath had a maximum photocurrent density of 9.28 mAcm-2 with an applied bias of + 1.0 V vs. Ag/AgCl electrode in contact with electrolyte containing 0.25 M K2SO3 and 0.35 M Na2S. The results show that high quality AgInS2 films can be deposited on FTO-coated glass substrates for photoelectrochemical (PEC) applications. Furthermore, the effect of the [Ga]/[In] molar ratio in the solution bath on the structure, morphology, and photoelectrochemical (PEC) properties of Ga-doped AgInS2 ([Ag]/[In]=0.8) films is also reported. X-ray diffraction (XRD) patterns of films reveal that the peaks of samples shifted to higher angles with increasing [Ga]/[In] ratio in the solution bath. The thickness, direct band gap, and indirect band gap of the samples were in the ranges of 643 to 580 nm, 1.84 eV to 1.93 eV, and 1.42 to 1.59 eV, respectively. The flat-band potentials of the films were in the range of -0.76 to -0.99 V vs. normal hydrogen electrode (NHE), as obtained using Mott-Schottky plots and open-circuit potential (OCP) measurements of samples. The maximum photoenhancement current density of 10.37 ± 0.13 mAcm-2 was obtained for Ga-doped AgInS2 films with a precursor ratio of [Ga]/[In] = 0.03 at an applied bias of +1.0 V vs. Ag/AgCl electrode in K2SO3 (0.25 M) and Na2S (0.35 M) aqueous solution.