| Summary: | 碩士 === 吳鳳科技大學 === 光機電暨材料研究所 === 102 === The main purpose of this study is to investigate the low-cost non-vacuum electrochemical coating methods in preparation of the precursor film the Cu(In1-x,Gax)Se2 (CIGS) absorber layer. To find the most suitable film growth conditions, we use two types of co-electrodepositions to grow Mo / SLG substrates: the constant potential electrodeposition and pulsed electrodeposition. The surface morphology, composition, and crystal structure analyses of the prepared CIGS thin films are performed by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD).
The experimental results show that the deposition potential (either in voltage or current) of co-electrodeposition significantly influences the precipitation of Ga (Gallium) elements on thin films. In addition, the constant current mode exhibites better deposition than the constant potential mode. Furthermore, the pH value of electrolyte makes no difference on the CIGS films composition. Moreover, the change of Se (Selenium) concentration in electrolyte can significantly vary the properties of the deposited films. When the concentration of Se is less than 15mM, the adhesion of the surface coating becomes weak.
During the pulse electrodeposition process, the change of the duty cycle (Ton and Toff) can affects greatly on the film quality of the CIGS film. When the duty cycle is less than 0.5, the grown film exhibits dramatic change in surface morphology and other material properties. In addition, varying deposition frequency also significantly can change the surface morphology of the deposited film. It is also found the secondary phase CuSe2 (copper selenide) can be suppressed when the concentration of Ga is 75 mM. Furthermore, the change in the deposition temperature does mitigate CIGS (112) peak shift problem.
Finally, this study concludes that pulse electrodeposition method is more suitable for controlling CIGS thin-film deposition and produces more stable film quality than the conventional constant current / constant potential deposition method is.
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