Thin films and solar energy applications

Abstract

Solar energy is diffuse (1 kW m 2 at sea level) and its large scale utilization will require covering very large areas with solar energy conversion devices. For example, to produce all the electrical energy consumed in the US today, about 10,000 km 2 of its area would need to be covered by devices which can convert sunlight into electricity with an efficiency of 10%. Economic considerations dictate that thin films will play a central role in the exploitation of solar energy. This paper will review the use of thin films in solar-thermal and solar-photovoltaic converters. In the former, thin film selective absorbers can increase the efficiency with which sunlight is transformed into heat. The problems of thermal absorber surfaces for concentrator systems will be discussed. In the case of solar-photovoltaic converters, the criteria for selection of appropriate semiconductors; grain size considerations; grain boundary problems: anti-reflection coatings and thin metal films in contacts will be discussed. The state of the art in selected thin film systems including the Cu x S/CdS cell; the indium tin oxide on silicon cell and the metal insulator silicon cell; the CuInSe 2/CdS and the amorphous silicon cell will be discussed.