Advanced Light Trapping for Hot-Carrier Solar Cells

Hot Carrier Solar Cells promise efficiencies way above Shockley-Queisser (SQ) limit, but are limited by the fast thermalization of the carriers. Ultra-thin solar cells can reduce this thermalization, but at the cost of a reduced absorption. We show light trapping can solve this issue, making the cell optically thicker, while electronically and phononically thinner. We introduce the multi-resonant absorption model, that pushes the light path enhancement limit by a factor π above Iambertian scattering. We then show that this enhancement provides a pure gain for hotcarrier solar cells, and that efficiencies significantly above the SQ limit can be obtained with realistic thermalization factors. Finally, we present a design to demonstrate that a hotter carrier population can be established in an absorber with light trapping.