Fabrication and analysis for zinc oxide nanorod anti-reflection layer on Cd-free CuInGaSe2 thin film solar cells

• Main Authors: Lin, Bing-Yi, 林秉誼
• Other Authors: Liu, Po-Tsun
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/51127764831704090774

碩士 === 國立交通大學 === 照明與能源光電研究所 === 102 === The Copper Indium Gallium Diselenide (CIGS) is the most promising material for solar cell application. Until now, the best conversion efficiency reaches 20.4% by EMPA, Swiss. However, the traditional buffer material is cadmium sulfide (CdS), the cadmium is toxic for environment. Thus the zinc sulfide (ZnS) was adopted for the alternative material for buffer layer in this thesis. On the other hand, the direct manner improved the conversion efficiency is application of anti-reflection layer. However, the traditional anti-reflection layer unable to reach broad-band anti-reflection due to the limitation of design. Thus, zinc oxide nanorod (ZnO NR) with graded refraction index was adopted for the anti-refleciton layer, and further improve the conversion efficiency of solar cell. For the ZnS buffer layer, we improved the deposition conditions consisted of initial point of deposition and mixed order of reactant and according to the growth mechanism in the chemical bath deposition, enhance the heterogeneous and suppress the homogeneous nucleation as possible to acquire the ZnS thin film with 100-nm-thick and 1.44-Zn/S ratio. For ZnO NR antireflection layer, we study the relationship between the height of ZnO NR and optical properties. We found the surface reflectance was reduced via the increase of height of ZnO NR but the transmittance was decreased accordingly. The absorption effect was proposed. After analyzing, the most promising period of ZnO NR growth for improvement of efficiency was between 8 and 14 minutes. Finally, we used ZnS as buffer layer and ZnO NR as anti-reflection layer for fabrication of CIGS solar cells. After analyzing the current-voltage characteristics, the CIGS solar cell with NR deposited for 11 minutes acquired the relative gains of conversion efficiency and short-circuit are 8.3% and 7.56%, respectively.