- Experimental evidence of enhancing the performance of ultra-efficient solar cells by external recycling of photon emission is presented – predicated on the strategy of increasing cell open-circuit voltage by reducing radiative recombination. It is equivalent to restricting the angular range of photon emission, and can only be effective in photovoltaics with high external luminescent efficiency. This has precluded the voltage enhancement from being observable in today's photovoltaic technologies. As shown here, however, it is attainable with the latest generation of champion single-junction one sun thin-film GaAs cells. The measurements are understandable in terms of basic photovoltaic thermodynamics.