Abstract: A light confining cavity collects much of the radiation reflected by a receiver, absorbing it imperfectly, and casts it again on the same receiver or on other receivers by means of an optical system. Only light in a bundle of rays of limited angular spread can escape from this cavity, which allows an entry aperture relatively large. Thus, the irradiance at the entry aperture may be low, and in some cases even lower than the irradiance at the absorber. In this way the requirements for the cavity materials and for the concentrating system feeding light to the cavity can be relaxed. The invention is of special interest in photovoltaic conversion devices because it improves the absorption of the solar cells and achieves higher conversion efficiency for photons of different energies by using solar cells of different materials.

Abstract: A planar solar cell photovoltaically active on both sides is positioned in a solar concentrator capable of simultaneously illuminating both sides of the cell. The cell is immersed in a transparent liquid that enhances solar energy concentration and aids in removing undesirable heat from the cell. The solar cell, having two photovoltaically active sides, can be constituted by a n+pn+ structure or by a n+pp+ structure. Electrically conductive metal grids serving as cathode and anode connections are formed on both sides of the cell. The grid apertures advantageously allow the light to enter into the appropriate semiconductor regions. In the case of a n+pn+ structure, window means in the n+ layers are provided to permit electrical contact between the anode grids and the p region. Solar cells with complementary dopings, for example p+np+, are also possible.