A concept for obtaining high energy-conversion efficiency in a solar photovoltaic system involves (1) concentration and spectral dispersion of sunlight and (2) use of several types of solar photovoltaic cells, each placed at its optimum location in the spectrum. The spectral dispersion and concentration of sunlight can be effected by use of mirrors or lenses combined with prisms. The photovoltaic cells can be of the conventional single-junction type, which cost less than do the more advanced multijunction cells.

Each Type of Photovoltaic Cell responds maximally in a unique part of the spectrum, thereby contributing to overall efficiency in the conversion of spectrally dispersed sunlight to electricity.

Preliminary experiments to demonstrate the feasibility of this concept were performed on several types of cells, using artificial sunlight and prisms that had not been optimized. On the basis of these experiments plus references to the literature, it has been estimated that an optimized system of this type could perform with an energy-conversion efficiency approaching 50 percent (see table). In contrast, the more-expensive multijunction solar cells yield efficiencies between 20 and 30 percent, while the efficiencies of conventional solar cells range from 11 to 19 percent in white light.

This work was done by Wayne Phillips of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com under the category, or circle no. 20 on the TSP Order Card in this issue to receive a copy by mail ($5 charge).

Refer to NPO-20354

This Brief includes a Technical Support Package (TSP).
Solar-Cell System With High Conversion Efficiency

(reference NPO20354) is currently available for download from the TSP library.

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This article first appeared in the January, 1999 issue of NASA Tech Briefs Magazine.

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