High Efficiency Lightweight Triple Junction GaAs Solar Cells

The significance of the innovation in this Phase II SBIR is the development of a low cost lightweight multi-bandgap GaAs semiconductor material for high efficiency multijunction solar cells for space applications. This effort will advance space solar cell development by improvements in the efficiency and weight of GaAs based solar cells. This will be accomplished by applying our lift-off process to a triple junction bandgap structure on GaAs substrates. The complete elimination of the GaAs substrate from the solar cell active area is the pathway to significant weight reduction. The triple junction structure will consist of lattice-matched InGaP, GaAs, and InGaAs (1.0 eV) cells to capture a majority of the solar spectrum in space. The efficiency target is 29% under 1 sun AM1.5 for the lifted-off solar cell. The cost reduction target is 50% using a combination of recycled GaAs substrates from the lift-off process and large area 6-inch GaAs substrates.