Development of Photovoltaics and Photo-detectors by a-SiGe Thin Film Technology

• Main Authors: Tsai, Yi-Shin, 蔡易昕
• Other Authors: Shieh, Jia-Min
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/73899781748623121377

碩士 === 國立交通大學 === 顯示科技研究所 === 102 === In this thesis, we investigate the performance of hydrogenated amorphous silicon germanium thin film which can be used in photovoltaics and photod-etectors fabricated by very high frequency plasma enhance chemical vapor deposition system. In order to utilize the solar spectra in near infrared regime and obtain higher quantum efficiency, but amorphous silicon thin film cannot efficiently absorb the solar spectra regime beyond 750nm since the optical band gap of amorphous silicon is about 1.8eV to 1.9eV. So we decided to dope germanium atom into silicon thin film to form amorphous silicon germanium, whose band gap can lower to 1.45eV （1.45eV~1.7eV）. In this article, we used the optical band gap about 1.55eV a-SiGe:H film to fabricate photovoltaics, whose conversion efficiency can reach 4.65% and the absorbing spectra of quantum efficiency can be broadened from 300~850nm.For the purpose of lowering the defect in the a-SiGe:H thin film, we chose disilane and germane as precursor rather silane and germane, since the components of the first combination（disilane and germanium）have similar deposition rate. The benefit of low defect a-SiGe:H thin film is easily extracting the electron-hole pairs after light exposure, causing higher short-circuit current density、conversion efficiency and quantum efficiency。 We also increase the photovoltaics’ thickness of absorption layer to obtain higher quantum efficiency at the near infrared regime。When the thickness goes up to 1μm，we can observe that the wavelength beyond 750 will raise obviously. So we can also use this component with proper absorption layer thickness as photo-detector. In the future, our research will focus on using hydrogenated amorphous silicon and silicon germanium thin film to fabricate a-Si/a-SiGe tandem photovolaics with high conversion efficiency and broad band quantum efficiency