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International Journal of Photoenergy
Volume 2015, Article ID 275697, 6 pages
Research Article

Improving Crystalline Silicon Solar Cell Efficiency Using Graded-Refractive-Index SiON/ZnO Nanostructures

1Institute of Microelectronics, Department of Electrical Engineering, National Cheng Kung University, Tainan 701, Taiwan
2Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 701, Taiwan
3Department of Electronics Engineering, Chung Hua University, Hsinchu 300, Taiwan
4Department of Electronics Engineering, National Chiao Tung University, Hsinchu 300, Taiwan

Received 24 November 2014; Accepted 30 December 2014

Academic Editor: Shyh-Jer Huang

Copyright © 2015 Yung-Chun Tu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The fabrication of silicon oxynitride (SiON)/ZnO nanotube (NT) arrays and their application in improving the energy conversion efficiency (η) of crystalline Si-based solar cells (SCs) are reported. The SiON/ZnO NT arrays have a graded-refractive-index that varies from 3.5 (Si) to (Si3N4 and ZnO) to (SiON) to 1 (air). Experimental results show that the use of 0.4 μm long ZnO NT arrays coated with a 150 nm thick SiON film increases by 39.2% under AM 1.5 G (100 mW/cm2) illumination as compared to that of regular SCs with a Si3N4/micropyramid surface. This enhancement can be attributed to SiON/ZnO NT arrays effectively releasing surface reflection and minimizing Fresnel loss.