Study of textured Al-doped ZnO thin films by wet-etching methods and application on front electrode of solar cell

• Main Authors: Kuo-ChanHuang, 黃國展
• Other Authors: Mau-Phon Houng
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/10399504904672644922

碩士 === 國立成功大學 === 微電子工程研究所碩博士班 === 98 === This study addresses the optimization of Rf magnetron-sputtered aluminum doped zinc oxide (ZnO:Al) thin films as the front contacts in silicon thin film solar cells. So this front contact has to exhibit low series resistance and high transparency in the visible light region (400–800 nm) to near-infrared (NIR) region (up to 1100 nm). Furthermore, it has to scatter the incident light efficiently in order to an effective light trapped inside the silicon absorption layer. In this research, ZnO:Al thin films were deposited on glass substrate by Rf magnetron-sputtered from a ceramic (ZnO 98wt%,Al2O3 2wt%) target. The surface texture is produced by wet etching treatment, here we chose three different solutions (hydrochloric acid, phosphoric acid, and nitric acid based combination) to observe the variation of surface morphology. We also focus on an optimized balance between electrical and optical properties need maintain a surface morphology well suited for light scattering and trapping. We also used the atomic force microscopy (AFM) measurement to evidence the haze factor which is related to amount of light scattering. As increase in haze is observed while the surface roughness (root mean square, rms) is increased. In this study, we achieve successfully a high transmission, high haze, and low resistivity TCO front contact thin film by wet etching treatment. The resistivity is approached to 5.47x10-4 Ωcm, the transmittance is approached to 75% and the haze is approached to 50%~60% in visible region, the higher haze is indicate that the more light is scattering form the texture, and more light will incident into the silicon absorption layer, it also can trap more light in the silicon absorption layer, it will effectively to improve the short circuit current (Jsc) for thin film solar cells. In our research, the short circuit current and energy conversion efficiency can enhance 1.84mA/cm2 and 1.07%.