Concepts for thin-film GaAs concentrator cells

The development of advanced GaAs concentrator solar cells for space power systems, and, in particular, the use of CLEFT (cleavage of lateral epitaxial films for transfer) processes for formation of thin-film structures is reported. The use of CLEFT has made possible processing of the back, and cells with back surface grids are discussed. Data on patterned junction development are presented; such junctions are expected to be useful in back surface applications requiring point contacts, grating structures, and interdigitated back contacts. CLEFT concentrator solar cells with grids on the front and back surfaces are reported. These cells are 4 μm-thick and are bonded to glass covers for support. Air mass zero efficiency of 18.8% has been obtained for a CLEFT concentrator operating at 18.5 suns