Electrical transport in boron‐doped polycrystalline zinc oxide thin films

Abstract

Abstract Boron doped Zinc oxide (ZnO:B) thin films are commonly used as transparent conductive oxide (TCO) in thin film silicon solar cells. TCO films with a high electrical conductivity combined with a high transparency are required for this application. In this paper, the electronic transport properties in polycrystalline ZnO:B grown by low pressure chemical vapor deposition (LPCVD) were investigated using Hall effect measurements and optical spectroscopy techniques. The systematic comparison between the optical mobility values deduced from the reflectance spectra using the Drude model, and the Hall mobility values, allowed us to clearly separate the respective influences on the electrical transport of potential barrier at grain boundaries and intragrain scattering. By analyzing the results for samples with large variation of grain size and doping level, we observed a continuous transition from grain boundary scattering to intragrain scattering. Finally, the stability of LPCVD ZnO:B in a humid environment was also investigated. The degradation of the electrical film properties due to damp heat treatment is analyzed and discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)