| Summary: | 博士 === 國立交通大學 === 電子工程學系 電子研究所 === 101 === In this study, we develop novel and cost-effective materials and techniques to enhance the performance of Si-based thin film solar cells.
We invent a new structure of band-gap engineering for hydrogenated microcrystalline silicon-germanium (μc-SiGe:H) single junction solar cells. μc-Si:H buffer layers are deposited between p-Si:H and μc-SiGe:H to reduce potential barriers due to the valence-band discontinuity. Moreover, we implement μc-Si:H field-enhancement layers (FELs) between n-Si:H and μc-SiGe:H to increase the built-in electric field in absorbers, which is demonstrated by the Atlas device simulation. Instead of increasing doping concentration in p-Si:H and n-Si:H layers, this technique can avoid the loss of incoming light. Here, we investigate the relation between the crystallinity and the thickness of FELs and the performance of solar cells. Compared with the traditional cells, the cells with optimized FELs show 19% and 28% enhancements in fill factor (FF) and conversion efficiency (η), respectively. Furthermore, a-Si:H/μc-SiGe:H tandem cells with optimized μc-Si:H FELs can reveal η of 11.48%. We also implement band-gap engineering in a-Si:H/μc-Si:H tandem cells. In order to further enhance light absorption efficiency in a short wavelength range in bottom cells, μc-Si:H layers with low crystallinity are deposited between p-Si:H layers and μc-Si:H absorbers. μc-Si:H FELs with different crystallinity and thickness deposited between n-Si:H layers and μc-Si:H absorbers are investigated. a-Si:H/μc-Si:H tandem cells can reveal η of 11.87% in a optimized condition.
Meanwhile, we successfully develop self-texturing ZnO:Ga (GZO) substrates for solar cells by an atmospheric-pressure plasma jet (APPJ) and sputtering. The electro-optical properties of the textured GZOs are mainly controlled by the haze of organosilicon underlayers deposited by the APPJ. In this study, we investigate the characteristics of organosilicon layers and texturing GZOs deposited in different process conditions. Moreover, light-trapping effects resulting from these textured substrates in Si-based thin-film solar cells are examined by the 3D finite-difference time domain (FDTD) simulation. In a optimized condition, a-Si:H single junction solar cells fabricated on homemade GZO substrates can exhibit η of 8.78%.
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