Description: The proposed innovation is the development of a technology that will enable the manufacture of high-efficiency (>40%), quadruple(4) junction solar cells on lightweight Ge substrates. We plan to achieve this objective by developing a new semiconductor alloy, InGaAsN, which will be employed as the 1.18 eV bottom cell in quadruple-junction [InGaP (1.8 eV) / GaInAs P(1.5 eV) / InGaAsN (1.18 eV) / Ge (0.67eV)] solar cells. The InGaAsN alloy material will be lattice matched to Ge, which is a clear improvement over existing inverted metamorphic (IMM) technology, specifically, the existing lattice-mismatched InGaAs 1.0 eV bottom cell is replaced with a lattice-matched InGaAsN 1.18 eV bottom cell. This eliminates the need to grow a thick graded buffer layer. Another advantage of this system is higher efficiency and higher reliability solar cells which can effectively be a drop in replacement to the existing Ge based space cells. At the end of this project, we expect to have developed and integrated InGaAsN - 1.18 eV material, which can be used in Ge-based multi-junction cells that have the potential to achieve efficiencies in excess of 40% at AM0, one sun illumination.

Benefits: Quadruple junction solar cells based on Ge can be directly adopted as drop in replacement to the existing Ge based triple junction cells. They would provide higher efficiency than the existing Ge technology and provide similar reliability. The 4-junction Ge based cells can be used for high radiation exposure orbits, Solar Electric propulsion (SEP) related applications for large Solar arrays, conventional Satellite Power applications.

The quadruple junction solar cells based on Ge substrates can be used in terrestrial applications such as for CPV, Mobile Solar Power applications such as battery charging and Solar arrays on UAV to extend the flight duration. Solar Power for Satellites- Military and civilian applications