The present state-of-the-art of photovoltaic solar energy conversion

Abstract

The present state-of-the-art in photovoltaic solar energy conversion, in particular, as applied for space vehicle power supplies is summarized. Past and future development goals are: lower weight-to-power and cost-to-power ratios, higher reliability, and increased useful lifetimes. Difficulties with photovoltaic solar energy converting devices were encountered in their classification based on exact determination of the power output and efficiency in “standard” sunlight, and by a reduction of their useful life expectancy due to radiation damage encountered in the Van Allen belts and in solar flares. Remedial actions in progress are outlined. Recent improvements introduced on the present standard device, namely, the silicon solar cell are discussed. They include application of metallic grids for the reduction of series resistance and change of the p-layer thickness for improved spectral response. Further, attempts to develop methods for preparing large area and thin film silicon solar devices are reviewed, and finally a survey is given of the progress made in the application of other semiconductor materials to solar photovoltaic energy conversion. Here the work on cadmium sulphide solar cells stands out due to the achievement of solar conversion efficiencies of up to 4 1 2 % on thin film cells.