| Summary: | 碩士 === 國立中山大學 === 電機工程學系研究所 === 102 === In this paper, we propose a series of amorphous silicon (a-Si) and amorphous silicon germanium (a-SiGe) heterojunction solar cells. The a-SiGe is inserted into the different junction of the conventional planar a-Si PIN solar cells thus the new different structures of solar cell,「p-a-Si:H / i1-a-SiGe / i2-a-Si:H / n-a-Si:H」、「p-a-Si:H / i1-a-Si:H / i2-a-SiGe / n-a-Si:H」、「p-a-Si:H / i1-a-SiGe / i2-a-Si:H / i3-a-SiGe / n-a-Si:H」and 「p-a-Si:H / i1-a-Si:H / i2-a-SiGe / i3-a-Si:H / n-a-Si:H」 are formed. Concerning that the conventional a-Si:H p-i-n structure has the high energy gap (1.7~1.9 eV) and high absorption coefficient,, the absorption layer thickness thus can be reduced for further reducing the cost. However, the high energy gap of a-Si:H cannot absorb long-wavelength of light so that the power conversion efficiency cannot be improved. In order to increase the long-wavelength absorption, we insert one or two layers of a-SiGe absorption layers into the conventional PIN counterpart due to the narrow energy gap (1.1~1.7 eV) of a-SiGe. The long-wavelength light can thus be more effectively absorbed and generate more carriers to increase the short-circuit current density (JSC). Therefore, the power conversion efficiency can be enhanced dramatically. The new designed a-Si/a-SiGe heterojunction solar cells improve short current density much significantly than conventional amorphous silicon solar cells do. Moreover, the power conversion efficiency of the new designed a-Si/a-SiGe solar cell is 16.29 %, which is achieved for the thin film solar cell up to now. Furthermore, for the purpose of enhancing the power conversion efficiency, we combine the 「p-a-Si:H / i1-a-SiGe / i2-a-Si:H / i3-a-SiGe / n-a-Si:H」 structure and the pillared array structure to optimize the design by using TCAD software. The results indicate that under the same solar cell structure, the pillared array structure has a higher power conversion efficiency which is 4.76 % more than that of the planar structure stated above.
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