Thin-film GaAs epitaxial life-off solar cells for space applications

In the present work the space compatibility of thin-film GaAs solar cells is studied. These cells are separated from their GaAs substrate by the epitaxial lift-off (ELO) technique and mounted behind a CMG cover glass which at the same time serves as a stable carrier for the thin film cells. In the present initial stage of development these cells have an average efficiency of about 15.4% under AM0 illumination due to not yet optimized grid contacts and anti-reflection coatings. Inspection after irradiation by 1 MeV electrons, thermal vacuum and thermal cycling experiments reveal that degradation of the cells is largely due to delamination and micro-cracking. Based on these results, glass dehydration and adhesive degassing procedures are implemented in the ELO cell processing. As a consequence, even in this premature phase, newly produced cells show a, radiation hardness comparable to or better than that of commercially available GaAs cells on Ge substrates and are virtually unaffected by severe thermal cycling. Copyright (c) 2005 John Wiley & Sons, Ltd.