Radiation-resistant and high-efficiency InGaP/InGaAs/Ge 3-junction solar cells

In this paper, radiation-resistant and high-efficiency III-V compound multi-junction (MJ) solar cells are presented. We have proposed wide-bandgap InGaP double hetero (DH) structure tunnel junction for cell interconnection and lattice-matched InGaAs middle cell. A world-record efficiency of 29.2% (AM0, 28°C) has been obtained for InGaP/InGaAs/Ge 3-junction solar cells (2x2cm²) fabricated by the MOCVD method. Furthermore, radiation effects on multi-junction solar cells have been studied for space applications. The authors have found superior radiation-resistance of InGaP-based MJ-cells and minority-carrier injection-enhanced annealing of radiation-induced defects in InGaP and InGaAsP sub cell materials in addition to those of InP cell materials found previously. We are now demonstrating effectiveness of InGaP-based MJ-cells using the MDS-1 satellite launched on February 4, 2002.