Development of coplanar back contact for large area, thin, GaAs/Ge solar cells

Abstract

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