| Summary: | 碩士 === 國立臺灣科技大學 === 材料科學與工程系 === 100 === In recent years, the vacuum processes for making Cu(In,Ga)Se2 (CIGSe) thin-film solar cells are gradually getting researchers’ attentions. There are many ways for vacuum processes. Evaporation and sputtering process are the most commonly used. In this experiment, we used sputtering vacuum process as our major process. At present, CIGSe solar cells with power conversion efficiency more than 20% have been made by co-evaporation process. When CIGSe films were prepared by metallic targets, there was a problem of Ga distribution. To overcome the Ga-distribution problem, the (Cu-In2Se3-Ga) target was used with the combined advantages of metallic target for larger deposited grains and the ceramic target for better phase stability. With these efforts, CIGSe films are expected to be dense and smooth and have a uniform composition distribution.
In this study, CIGSe absorption layers for thin-film solar cells were deposited by using DC-sputtering with the cermet targets on sodium lime glass substrates, followed by a two-step selenization procedure. The cermet targets formed the films containing ceramic and metallic phases. With the cermet method, the problem of Ga distribution was solved. The variations of materials performance and properties for CIGSe films with sputtering and selenization temperatures were investigated with the aids of FE-SEM, XRD, EDS, and Hall effect measurement. The CIGSe solar cell devices were constituted with the stacking form of Na glass/ Mo/CIGSe/CdS/ZnO/ITO/Ag. The power conversion efficiency of the solar cell device is evaluated under the standard AM 1.5 illumination.
The experimental results showed that the CIGSe films obtained with the (Cu-In2Se3-Ga) target followed by a two-step selenization process at 600 oC for 1 h were dense and had the desired composition and the grain size of 1-2 μm. The stacked solar cell devices displayed the power conversion efficiencies of 0.42% and 0.55% for the cells with the CIGSe absorption layers after one-step and two-step selenization processes, respectively.
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