Nanostructured amorphous silicon solar cells

• Main Authors: Wei-Chen Tu, 涂維珍
• Other Authors: 李嗣涔
• Format: Others
• Language: en_US
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/34730645703932391407

博士 === 國立臺灣大學 === 電子工程學研究所 === 100 === Within various-material solar cells, silicon is nontoxic and the second most abundant element in the earth’s crust. Moreover, due to the need of low-cost and low-temperature fabrication processes, amorphous silicon (a-Si) with a high absorption coefficient in the visible range of the solar spectrum opens up many opportunities for thin-film solar cells. Therefore, a-Si is chosen as an active layer of solar cells in the dissertation. However, an issue that has caused considerable amount of debate is the short minority carrier diffusion lengths of a-Si. Therefore, the objective of the research is to improve the performance of a-Si solar cells by several nanostructured designs as described below. 1. Hydrogenated amorphous silicon solar cell on glass substrate patterned by hexagonal nanocylinder array Plasmonic nanostructured amorphous silicon solar cells were accomplished by nanosphere lithography. The hexagonal silver nanostructure acted as a back reflector exhibits surface plasmon resonance and light scattering thereby the electrical field surrounding Ag film and the light path length within the cell are enhanced. For these reasons, the improved short-circuit current and power conversion efficiency are realized. The best performance of the patterned solar cell with period of 450 nm and etching time of 17 minutes was achieved with 25% enhancement in η compared as flat solar cell. 2. Tunable surface plasmon resonance and improved light scattering in amorphous silicon solar cells by double-walled carbon nanotubes To further optimize the effect of surface plasmon resonance on efficiency of solar cells, double-walled carbon nanotubes coated with polymer on periodic Ag array was carried out to achieve the goal. By coating different-density DWCNTs, the surface plasmon resonance is red-shifted and the light scattering is enhanced at identical wavelength region. Compared with the reference cell, the cell with DWCNTs yields an improved JSC of 14.07 mA/cm2 and η of 6.55%. With this fast and fine-tuned surface plasmon resonance, it will create more opportunities to various-material solar cells such as polycrystalline and microcrystalline silicon or organic solar cells. 3. Hexagonal nanohole array on ITO films for antireflection coatings Besides the nanostructure on back reflector, one can improve performance of optical devices by textured antireflection coating with reduced reflection of incoming photons. Therefore, special attention is given to the hexagonal nanohole array on indium tin oxide films. An optimized reflectance is obtained by 280 nm-diameter nanohole array on ITO, which shows a maximum reduction of 56.7% in total reflectance at wavelength of 562 nm. Such nanohole fabrication processes expand the possibility for various device applications.