Luminescent coupling in planar opto-electronic devices

Effects of luminescent coupling are observed in monolithic 5 V, five-junction GaAs phototransducers. Power conversion efficiency was measured at 61.6% ± 3% under the continuous, monochromatic illumination for which they were designed. Modeling shows that photon recycling can account for up to 350 mV of photovoltage in these devices. Drift-diffusion based simulations including a luminescent coupling term in the continuity equation show a broadening of the internal quantum efficiency curve which agrees well with experimental measurements. Luminescent coupling is shown to expand the spectral bandwidth of the phototransducer by a factor of at least 3.5 for devices with three or more junctions, even in cases where multiple absorption/emission events are required to transfer excess carriers into the limiting junction. We present a detailed description of the novel luminescent coupling modeling technique used to predict these performance enhancements.