Bismuth doped ZnO films as anti-reflection coatings for solar cells

Abstract

For fabrication of zinc oxide-based optoelectronic devices, especially solar cells, the development of cost-effective and low-temperature synthesis techniques for the deposition of high quality ZnO films is paramount. In this paper, incorporating Bi-doped ZnO films was prepared by the sol-gel spin coating method. The optical constants of the prepared thin films depend on the synthesis conditions. XRD measurement show that a high quality of ZnO:Bi nanostructure have preferably grow along (002) direction. The ZnO:Bi thin films were fabricated as antireflection coatings (ARCs) for solar cells. The nanoscale morphology altered through the different Bi content in the films, has a great effect on the macroscopic ARC performance. The optical constants as refractive index and extinction coefficient are determined through the transmittance and reflectance spectra. Textured ZnO:Bi films with average thickness ranging from 87 nm to 94 nm present a broadband reflection suppression from 400 to 1100 nm wavelength. The refractive index around 1.31-1.47 estimated is appropriate to an ARC layer for Si solar cells.