| Summary: | 博士 === 國立臺灣科技大學 === 化學工程系 === 106 === Cu2ZnSnS4 (CZTS), which owning suitable bandgap and band position, high absorption coefficient, is a suitable sensitizer for photovoltaic or photoelectrochemical (PEC) application. In this study, CZTS nanoparticles were decorated on TiO2 NRAs with adhesion layer by using solvothermal method. Different kinds of adhesion layers, such as CdS, CuS, Cu2S, were employed to enhance the uniformity of CZTS. Finally, ZnS layer was used as passivation layer for increasing conversion efficient. By using Cu2S adhesion layer and ZnS passivation layer, the photocurrent density of TiO2/Cu2S(6)/CZTS/ZnS(5) electrode can reach 5.81 mA/cm2 @1.23 V vs RHE. According to electrochemical impedance spectroscopy (EIS) analysis, the Cu2S adhesion layer assisted the charge separation in CZTS due to the cascade band structure, and the ZnS passivation layer helped the photogenerated hole transfer from CZTS to the electrolyte. Besides, the stability of the CZTS in the electrolyte solution is one of the major problems for long time usage. To further improve the stability as well as the PEC performance of CZTS sensitized TiO2 electrode, the ZnS and SiO2 dual passivation layers are employed to passivate the surface of the CZTS. The tafel measurement and electrochemical impedance spectroscopy are used to understand the mechanism of the SiO2 over layer. After the SiO2 decoration, the activity of the device decrease a little and the surface state chemical capacity also decrease. Therefore, the SiO2 Over layer seems to be a surface passivation layer, which can passivate the surface defect and increase the efficient of the device. The photocurrent of the device with ZnS and SiO2 dual passivation layers can reach 7.92 mA/cm2 @1.23 V vs. RHE. The photocurrent density of the photoelectrode with dual passivation remained 82% of its initial value after 4 hours measurement.
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