High Rate Deposition of Transparent Conducting Zinc Oxide Using Activated Oxygen for Photovoltaic Manufacturing Cost Reduction

41340 November 20, 1996 Energy Photovoltaics, Inc. The conventional method of preparing a thin film, zinc oxide transparent conductor is radio frequency magnetron sputtering from a ceramic target. The cost of this approach for coating copper/indium/selenium photovoltaic modules in a high volume plant is prohibitive and the deposition rate too slow. This project proposes to demonstrate the formation of high quality zinc oxide (ZnO)/aluminum(Al) transparent conductors by linear, reactive, activated evaporation of zinc. High rate Zn sources will be developed, and the Zn will be oxidized by atomic oxygen formed by dissociation of molecular oxygen in a high intensity discharge. Low temperature doping will be accomplished by use of a non-toxic, Al-containing metalorganic. Films will be characterized by Rutherford backscattering, particle-induced X-ray emission, X-ray diffraction, X-ray photoelectron spectroscopy and conventional electrical and optical techniques. The compatibility of the ZnO process in producing state-of-the-art photovoltaic devices will be verified. Following initial demonstrations with point sources, novel linear sources for the Zn, O, and dopant will be developed capable of a coating width up to 0.5 m for large area coating with substrate translation. The distinguishing features of this method are a) the very low cost of the source materials, b) the ability to independently control the Zn, O, and dopant fluxes, c) the line source nature of the deposition heads, and d) potentially very high deposition rates. Anticipated Results/Potential Commercial Applications as described by the awardee: High quality transparent conducting coatings of ZnO:Al from inexpensive source materials, at rates far exceeding current practice, and from linear sources for large area coating, is anticipated. Successful manufacture of ZnO:Al using this process would allow cost reduction for thin film photovoltaics. The process could also be utilized in the production of energy-saving glass, electromagnetic interference barrier coatings, and flat panel displays.