No abstract

The Space Station Freedom Solar A m y Program is required to provide a 75 kW power module that uses eight solar array (SA) wings over a four-year period in low Earth orbit (LEO). Each wing will be capable of providing 23.4 kW at the 4-year design point. LMSC is providing the flexible substrate SAs that must survive exposure to the space environment, including atomic oxygen, for an operating life of fifteen years. Trade studies and development testing, important for evolving any design to maturity, are presently underway at Lockheed Missiles & Space Company, Inc. (LMSC) on the flexible solar array. The trade study and development areas being investigated include solar cell module size, solar cell weld pads, panel stiffener frames, materials inherently resistant to atomic oxygen, and weight reduction design alternatives.

This paper describes development of large area (26x6 cm), thin ( < 6 mils), high efficiency GaAs solar cells on Ge substrates with coplanar back contacts. Over three hundred solar cells have been fabricated to date, to identify process issues and to demonstrate a production capability.Key process areas of concern were edge rounding and deposition of high quality continuous dielectric layers around the cell edges. Several edge rounding techniques and various dielectric deposition techniques were evaluated to identify the best dielectric system. Using improved dielectric layers and edge rounding techniques, large area (6x6 cm), wraparound GaAs/Ge solar cells with an AM0 efficiency up to 17.4% have been obtained.Smaller area (4x4 cm) wrapthrough GaAs/Ge solar cells showed an AM0 efficiency of 18.0%. BACKGROUND