GaAsN/GaAsSb superlattices as 1 eV layers for efficient multi-junction solar cells

We demonstrate type-II GaAsSb/GaAsN superlattices as a suitable candidate to form a lattice-matched 1.01.15 eV subcell that could significantly improve the performance of multi-junction solar cells. The spatial separation of N and Sb allows better lattice-matching control, composition homogeneity, crystal quality and interface abruptness. Moreover, the type-II band alignment provides effective bandgap and radiative lifetime tunability through the period thickness. For the impact of period thickness on transport, quantum-kinetic simulations support the experimental finding of efficient carrier extraction at thicknesses up to 6 nm. All this leads to single-junction solar cells with improved efficiency under monochromatic illumination over the equivalent bulk devices.