Next-Generation 30-45% Efficient Multi-Junction Solar Cell

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.