A Review of NREL Research into Transparent Conducting Oxides
Since the 1980s, many of the successes in photovoltaic (PV) research at the US National Renewable Energy Laboratory have been assisted by improved fundamental understanding and advanced synthesis techniques for various transparent conducting oxide (TCO) materials. In this chapter, we review some of these TCO materials, describing not only the degree to which our understanding has improved over the past ∼30 years, but also with a view to indicating where we believe significant advances remain possible. These TCO materials are discussed within the context of their specific PV device application, and include the primary and relevant alloy oxides of indium, zinc, tin and cadmium. Additionally, because the PV application could eventually become the primary use of many of these oxides, the chapter also presents some discussion on issues related to mineral abundance and toxicity.