Graded Superlattice and Resonantly Coupled Quantum Wells for Dilute Nitride Solar Cells with Open Circuit Voltages that Exceed that of the Absorber’s Radiative Limit

The presentation focuses on the use of quantum engineered dilute nitride solar cells to alleviate minority carrier lifetime/ poor carrier collection issues encountered in these devices and aims at identifying novel pathways toward the development of high efficiency tandems. First and within the frame work of 1 to 1.2 eV III-V dilute nitride solar cells we will stress the strength of the carefully designed quantum engineered dilute nitride absorbers for achieving near unity photo-generated carrier collection. We will then show experimentally the possibility of realizing devices with open circuit voltages that approach or surpass the radiative limit (Woc= Eg-Voc~0.4 eV), The latest is achieved by developing thin barrier GaAsN/GaAs super-lattices in the intrinsic region and here we demonstrate a record open circuit voltage having Woc=Eg/q-Voc~0.24, that exceed the perceived radiative limit thus set the highest value reported in the literature for dilute nitride solar cells and set a pathway for extending the multijunction solar cell efficiencies to beyond 50%.