Application of ZnO Single Crystal Rods as Anti-Reflective Material for PV Cells

Abstract

In this study, ZnO nanorods for antireflection coatings application to the silicon solar cells were epitaxially grown over the Si substrate using both thermal evaporation method and wet chemical method and their characteristics were investigated. A precursor for the thermal evaporation method was prepared by impregnating zinc acetate over the activated carbon at three different loading amounts: 10, 20, and 30 wt%. The temperature for the epitaxial growth of ZnO nanorods over the substrate was fixed to 850°C. The diameter of the synthesized single crystalline ZnO nanorods was about 1 μm. The shape and size of the ZnO nanorods varied with the content of the precursors loaded over the activated carbon. The length of the ZnO nanorods increased as the loading amount of the zinc was increased. Single crystalline ZnO nanorods were grown over the substrates by a hydrothermal synthesis in an autoclave reactor. Zinc nitrate was used for the precursor material in the wet chemical method. The length and diameter of the ZnO nanorods synthesized by the wet chemical method were about 200 nm and a few nm, respectively. The surface morphology of the ZnO nanorods prepared by two growth methods was observed by scanning electron microscope. Its crystal structure was analyzed by an X-ray diffraction spectrometer. The optical properties, such as reflectance, were measured by the UV-Visible spectrophotometer. It was confirmed that ZnO nanorods decrease the reflectance of UV and Visible lights. Therefore, it was concluded that ZnO nanorods can be used as the antireflective material for photo voltaic cells.

Keywords:

• antireflection coatings
• zinc oxide nanorods
• solar cells
• thermal evaporation method
• wet chemical method

Acknowledgement

This work was supported by the 2011 Yeungnam University Research Grant and the Human Resources Development Program of Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant (No 20104010100580) funded by the Korean Ministry of Knowledge Economy.