Investigation of V doped ZnO transparent conductive oxide films

Abstract

The performance of the ZnO film that is an indispensable part of pin-type Si-based thin-film solar cells, plays a crucial role in high-efficiency thin-film solar cells and also forms a significant part in photovoltaic research and development. In this paper, low resistivity and wide broadband spectrum transmittance vanadium (V) doped ZnO (VZO) films are successfully fabricated on Corning XG substrates at various substrate temperatures (STs). The properties of VZO films are investigated by the radio-frequency magnetron sputtering technique and plane wave pseudo-potential method based on the density-functional theory. The experimental results demonstrate that all the VZO flms have (002) preferred orientation with the c-axis perpendicular to the substrate, and the crystalline quality is found to increase with the substrate temperature (ST) rising up to 280 ℃ and decrease when the ST increases further. The optimal VZO film is achieved at 280 ℃ with a resistivity of 3.810-3 cm and an average transmittance of more than 85% in a range of 500-2000 nm. The theoretical result shows that after incorporation of V the Fermi level goes through the conduction band, showing a typical n-type metallic characteristic. The carriers originate from the orbits of V 3d and O 2p. The calculated lattice constants and mobility for VZO film are in agreement well with the experimental results. The consistency of the theoretical results with the experimental results shows that the VZO thin film has a great potential application as a front contact in high-efficiency thin film solar cells.