Lightweight InP Solar Cells for Space Applications

The innovation in this Phase I SBIR is the development of a technology which will enable the manufacture of a lightweight, low cost, InP based compound semiconductor material containing high efficiency multijunction solar cells suitable for deployment in very high altitude, very long endurance solar aircraft. The key technological step is the application of a production-worthy epitaxial liftoff (ELO) process to a multijunction solar cell structure fabricated on a large area InP substrate. Our focus will be on InP-based solar cells, in particular lattice-matched dual junction solar cell of InP and InGaAsP materials, because of the demonstrated radiation hardness of these materials. We will develop a road map towards InP solar cells capable of >30% conversion efficiency under AM0 illumination. We will also design a process by which thin epitaxial InP solar cell layers will be transferred onto very flexible conductive or non-conductive substrates. The resulting solar cell structures are expected to have a specific power >600 W/kg, to be capable of operating over temperatures in the range -80 ºC to 120 ºC and to have excellent reliability while exposed to space radiation levels