Study of Light Trapping Effect for Subwavelength-Structured Optical Disc

• Main Authors: shang-Jung-Hsieh, 謝尚融
• Other Authors: 施錫富
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/53917491168817628847

碩士 === 國立中興大學 === 機械工程學系所 === 96 === This study is to compare the subwavelength-structured effects of optical discs on antireflection and light trapping, and apply them to solar cell applications. By increasing the diffraction angle to the critical angle of total internal reflection, the absorption length can be extended and the absorption rate can be enhanced. Through the simulation of the vector diffraction theory, we analyzed the effects of the subwavelength-structured surfaces corresponding to different duty cycle and depth for antireflection. The trend of decreasing reflection was discussed while the subwavelength-structured surface was applied to the amorphous silicon (a-Si) thin film. The experimental results show that the antireflection coating and subwavelength structure on a substrate can decrease the average reflection from 9.6% to 4.5% in the wavelength range of 500nm to 1000nm. By depositing the a-Si thin film on the unstructured substrate, which acts as a silicon active layer in the thin-film solar cells, the average absorption is 55.3% in the wavelength range of 650nm to 1000nm. It increases to 62.2% if only the antireflection film is coated on its surface, to 73.8% if the subwavelength-structured surface is used, and to 84.3% if the metal reflector is deposited. Finally, the average absorption is above 85% if the transparent conducting film is also deposited between the subwavelength-structured surface and a-Si thin film.