Experimental demonstration of enhanced photon recycling in angle-restricted GaAs solar cells

For cells near the radiative limit, optically limiting the angles of emitted light causes emitted photons to be recycled back to the cell, leading to enhancement in voltage and efficiency. While this has been understood theoretically for some time, only recently have GaAs cells reached sufficient quality for the effect to be experimentally observed. Here, as proof of concept, we demonstrate enhanced photon recycling and open-circuit voltage (V-oc) experimentally using a narrow band dielectric multilayer angle restrictor on a high quality GaAs cell. With angle restriction we observe a clear decrease in the radiative dark current, which is consistent with the observed V-oc increase. Furthermore, we observe larger V-oc enhancements for cells that are closer to the radiative limit, and that more closely coupling the angle restrictor to the cell leads to greater V-oc gains, emphasizing the optical nature of the effect.