Photovoltaic Cells for Very High Altitude Very Long Endurance Solar Aircraft

The significance of the innovation in this Phase I SBIR is the development of a technology which will enable the manufacture of a light weight, low cost cost , multi-band gap compound semiconductor material containing high efficiency compound semiconductor multijunction solar cells suitable for deployment for in very high altitude, very long endurance (HALE) solar solar aircraft. This will be accomplished by applying a production production-worthy Epitaxial epitaxial Lift lift-off (ELO) process to a multi- band gap junction solar cell structure fabricated on a large area GaAs substrates. These efficient solar cell structures will be removed from the substrate in the form of a thin film and will be attached to lightweight, flexible carriers suitable for mounting on an aircraft wing. Low cost can be achieved due to the recycling of the GaAs substrate after the lift-off is performed Our focus will be focus will be given to GaAs-based solar cells and , in particular lattice-matched and highly disordered InGaP materials, because of the demonstrated efficiency of these structures. We will provide a clear path towards realizing develop a solar cell design capable of >30% efficiency target under AMAir Mass 1.5 illumination at 1 sun conditions. We will also define design a process where by which thin epitaxial layers will be transferred onto very a flexible conductive or non-conductive substrates. The resulting solar cell structures are expected to have an array mass density of <325 g/m2, and to be capable of operating for long durations in a 60 knot airflow at 100,000 feet.