GaAs solar cells grown on Si substrates for space use

GaAs single-junction and InGaP/GaAs multi-junction thin-film solar cells fabricated on Si substrates have great potential for high-efficiency, low-cost, lightweight and large-area space solar cells. Heteroepitaxy of GaAs thin films on Si substrates has been examined and high-efficiency GaAs thin-film solar cells with total-area efficiencies of 18·3% at AM0 and 20·0% at AM 1·5 on Si substrates (GaAs-on-Si solar cells) have been fabricated. In addition, 1-MeV electron irradiation damage to GaAs-on-Si cells has been studied. The GaAs-on-Si cells are found to show higher end-of-life efficiency than the conventional GaAs cells fabricated on GaAs substrates (GaAs- on-GaAs cells) under high-fluence 1-MeV electron irradiation of more than 1 × 1015 cm−2. The first space flight to make use of them has been carried out. Forty-eight 2 × 2 cm GaAs-on-Si cells with an average AM0 total-area efficiency of 16·9% have been evaluated in the Engineering Test Satellite No.6 (ETS-VI). The GaAs-on-Si cells have been demonstrated to be more radiation-resistant in space than GaAs-on-GaAs cells and 50, 100 and 200-μm-thick Si cells. These results show that the GaAs-on-Si single-junction and InGaP/GaAs-on-Si multi-junction cells have great potential for space applications. Copyright © 2001 John Wiley & Sons, Ltd.