Luminescent coupling in planar opto-electronic devices

Abstract

Effects of luminescent coupling are observed in monolithic 5 V, five-junction GaAs phototransducers. Power conversion efficiency was measured at 61.6% 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. V C 2015 AIP Publishing LLC. [http://dx

Nonradiative lifetime extraction using power-dependent relative photoluminescence of III-V semiconductor double-heterostructures

“…The scattering-matrix based optical model has previously been adopted to simulate the effects of photon recycling and luminescent coupling in solar cells. 20,24 It is also comparable to that published by Wilkins et al 25 to model luminescent coupling in planar opto-electronic devices. Fig.…”

“…The indirect bandgap of Al 0.75 Ga 0. 25 As corresponds to the X-band, which has a 300 meV conduction band offset with respect to GaAs, 29 and increases to nearly 600 meV due to dopinginduced band bending. In comparison, the indirect band of GaAs (L-band) is separated from the C-band by 285 meV.…”

Measurement of strong photon recycling in ultra‐thin GaAs n/p junctions monolithically integrated in high‐photovoltage vertical epitaxial heterostructure architectures with conversion efficiencies exceeding 60%

“…Finally, the I sc value of such PV devices can be most simply determined by the responsivity of the heterostructure ( R , in A/W), with I sc = R × P in , where P in is the input power of the optical source. In this study, we demonstrate experimentally that strong photon coupling and recycling effects are making important contributions to the responsivity of the VEHSA devices, particularly when the optical input is detuned from the peak of the spectral response. The device details have been published previously but here we show that this effect is especially beneficial for the VEHSA structures given that all the subcells have the same relative absorption characteristics.…”

Pushing the limits of concentrated photovoltaic solar cell tunnel junctions in novel high‐efficiency GaAs phototransducers based on a vertical epitaxial heterostructure architecture

“…Furthermore, the spectral response of the phototransducer has been found to be relatively broad because, at least in part, of photon reabsorption effects in the optically coupled thin structures. A detailed study of the spectral response of the phototransducers has indeed been providing interesting insight in the luminescent coupling effects present in these devices and is the subject of another publication [37].…”