We will demonstrate novel, Si-based technology for ultra-lightweight, high-efficiency, triple junction solar cells. Next-generation satellites require increased payload mass and power budget capabilities. Ultra lightweight, 40% efficient solar cells employing Silicon substrates will reduce array size and solar cell payload mass while still enabling power level scale-up. Our advanced, next generation design will enable extremely high efficiency by using materials with ideal band gaps for efficient solar cells. By employing Si substrates (> 2x lower density than Ge), solar cell payload mass will be reduced by more than two times over current Ge-based technology. Current state-of-the art solar cell technology employs tandem Ge/GaAs/InGaP junctions on Ge substrates. This approach has shown promise for 40% converstion efficiency by employing 1.0 eV InGaAsN material as an intermediate cell between Ge and GaAs. However, InGaAsN has shown fundamental limitations due to the presence of deep level traps. A new alternative Si-based approach could result in similar 40% efficiencies in addition to substantially lower weight and cost. Silicon has a 1.1 eV bandgap, significantly lower cost and weight than Ge, and provides superior mechanical stability and radiation hardness.
Benefits: The primary anticipated benefit is the development of a new Si-based solar cell technology for application in next generation satellites used by the US Air Force. We will develop ultra lightweight, 40% efficient solar cells employing Silicon substrates. Our advanced design will enable extremely high efficiency by using materials with ideal band gaps for efficient solar cells, and the use of Si substrates (Si has > 2x lower density than Ge) will reduce the solar cell payload mass by more than two times over current Ge-based technology. In addition to space-based applications, we anticipate commercial potential for terrestrial solar cells. By employing Si substrates this approach combines the low cost of Silicon technology with the high efficiency of Ge-based tandem solar cells.
Keywords: Solar Cell, Silicon, GaP, GaAsNP, Triple Junction, High-efficiency, Lightweight, Satellite
