A Novel Poly-Si Solar Cell using Grain Boundary Etching Treatment and Transparent Conducting Oxide

Abstract

This paper deals with a novel structure of polycrystalline silicon (poly-Si) solar cell for terrestrial applications. Grain boundary (GB) in poly-Si degrades a conversion efficiency of poly-Si solar cell. To reduce the GB side-effect, we investigated various parameters such as the preferential GB etch, etchtime, ITO electrode, heat treatment, and emitter layer effect. Among various preferential etchants such as Sirtl, Yang, Secco, and Schimmel, a Schimmel etchant illustrated an excellent preferential etching property. We observed a 10μm deep trench along grain boundaries and randomly textured grain surface with pyramid structure. We used rf magnetron sputter grown tin doped indium oxide (ITO) film as a top contact metal. ITO films showed a resistivity of 1.14 ×10-4 Ω-cm and transmittance of 90.5% for the wavelength of 594 nm. ITO films served as a top electrode as well as an effective AR coating layer. ITO film properties were strongly influenced by the preparation temperatures. Substrate temperature of 400oC gave the highest conversion efficiency of poly-Si solar cell. With well-fabricated poly-Si solar cells, we were able to achieve conversion efficiency as high as 16% at the input power of 20 mW/cm2.