1-5. Gallium Arsenide Technologies in Photovoltaic Conversion P. A. ILES, Y. C. M. YEH & F. HO Summary This paper describes how GaAs technology has been applied to manufacture high efficiency solar cells for use on spacecraft. Improved substrates, layer growth and cell fabrication processes have been combined to demonstrate that GaAs cells can provide some attractive options for spacecraft power designers and can be supplied at the required production levels. To penetrate this highly conservative market has required steady development for about ten years, and this development work is demonstrating promise for wider use of GaAs-based cells. Introduction For over 30 years, Silicon (Si) solar cells have provided electrical power for most spacecraft. Cell performance has increased steadily, and the cells have met increasing demands on output and reliability. GaAs cells have advantages over Si cells, including higher efficiency (around 25% more) and increased resistance to damage from particle impact. Unlike Si cells, there is no need to trade off high efficiency for high radiation resistance. In addition, GaAs cells have less fall-off in power when operating at high temperatures. GaAs solar cell arrays have been used on some Soviet satellites since the 1960s. Also in the 1960s RCA workers successfully made GaAs cells, but the difficulties in controlling GaAs crystal growth and cell processing did not warrant the additional costs required for manufacture. Milestones in Technology Development Advances in the 1970s In this period, work at IBM, Rockwell and Carnegie-Mellon University led to significant improvements in the performance and understanding of GaAs cells. In the late 1970s, US Air Force (USAF) contract work at Hughes Research Laboratories using liquid phase epitaxy to grow the GaAs layers demonstrated that efficiencies up to 19% could be obtained, that scale-up was possible, and that GaAs cells could meet most of the array requirements. P. A. Iles, Y. C. M. Yeh and F. Ho, Applied Solar Energy Corporation, City of Industry, CA 91749, USA. Paper number IAF-ICOSP89-1-5.
RkJQdWJsaXNoZXIy MTU5NjU0Mg==