| Summary: | 碩士 === 國立中央大學 === 能源工程研究所 === 98 === Chemical bath deposition (CBD) is applied to deposit Ag-In-S-Se quaternary compound photoelectrode thin film on indium tin oxide coated glass (ITO), which can then be used as the photoelectrode in photoelectrochemical production of hydrogen. The advantages of chemical bath deposition are simple, inexpensive and large area deposition. Besides, Ag-In-S-Se quaternary compound can absorb ultraviolet and visible light so that it has potential to develope. In our experiment, we investigate the crystal structure, morphology, optic property, and PEC performance as precursor ratio, bath temperature, ph value, number of thin film, stirring rate, thermal treatment temperature and atomic percentage of selenium are changed. The results of XRD and EDS show that AgIn5S8 is obtained when [Ag+]/[In3+] =1/5 and transformed to AgIn5S8-xSex quaternary compound by doping selenium with the direct band gap decreasing from 1.79 eV to the range of 1.75~1.786 eV. Both are identified as n-type semiconductor according to Mott-Schottky measurement with decreasing flat band potential from -0.78 V to -0.93 V(vs. Ag/AgCl) and increasing carrier density from 2.58×10^10 cm-3 to 2.83×10^12 cm-3. In PEC measurement, we use 0.25M K2SO3 and 0.35M Na2S as sacrificial reagent and 100 mW/cm2(AM 1.5G) simulation sunlight as light source. The photocurrent density of AgIn5S8 and AgIn5S7.992Se0.008 is 0.8 mA/cm2 and 1.15 mA/cm2 with an external voltage of 0V(vs. Ag/AgCl) respectively. Moreover, the result of stability test shows that photocorrosion phenomenon is inhibited by covering TiO2 on AgIn5S8-xSex photoelectrode thin film, and reduces 3.57% decay of photocurrent density.
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