Tunneling through GaAs-Ge superlattices for high efficiency solar cells

Tunneling currents in superlattice-based solar cells for high efficiency are major conduction mechanism in addition to thermal carrier escape. We propose a model for GaAs/Ge mqw structures, through which, tunneling current can be found as function of device geometry (quantum well and barrier width) Fermi energy and conduction band offset. Our model is adoptable to any mqw structure in the intrinsic region of pin solar cells. High short circuit currents are computed based on a tunneling model that includes device parameters, solar photon incidence and open circuit voltage. Under one sun, and at room temperatures, we predict tunneling currents in excess of 30mA/cm² for GaAs-Ge multijunction mid region of pin III-V solar cell structure. The total unit (top and bottom cell) is a high efficiency solar cell (in excess of 40%) with a 28% top cell and a 22% bottom cell.