Ultrahigh efficiencies in vertical epitaxial heterostructure architectures

Abstract

Optical to electrical power converting semiconductor devices were achieved with breakthrough performance by designing a Vertical Epitaxial Heterostructure Architecture. The devices are featuring modeled and measured conversion efficiencies greater than 65%. The ultrahigh conversion efficiencies were obtained by monolithically integrating several thin GaAs photovoltaic junctions tailored with submicron absorption thicknesses and grown in a single crystal by epitaxy. The heterostructures that were engineered with a number N of such ultrathin junctions yielded an optimal external quantum efficiencies approaching 100%/N. The heterostructures are capable of output voltages that are multiple times larger than the corresponding photovoltage of the input light. The individual nanoscale junctions are each generating up to ∼1.2 V of output voltage when illuminated in the infrared. We compare the optoelectronic properties of phototransducers prepared with designs having 5 to 12 junctions and that are exhibiting voltage outputs between >5 V and >14 V.

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%

“…Furthermore, high photovoltages and conversion efficiencies have been reported with GaAs side by side planar or vertical arrangements, in particular at high optical intensities with light management or in other material systems . Moreover, record‐high photovoltages and unprecedented monochromatic conversion efficiencies have now been demonstrated for phototransducer applications with the vertical epitaxial heterostructure architecture (VEHSA) design which is engineered with multiple thin, partially absorbing, subcells of the same material . The monolithic epitaxial design of the VEHSA devices naturally allows to construct n/p junction devices with exceptionally low shunting and series resistance issues.…”

On the temperature dependence of dual‐junction laser power converters

“…Another technological approach is based on monolithic integration. This can be implemented by lateral segmentation (multi-segment cell, also known as monolithic interconnected module or MIM) [10][11][12] or by vertical stacking of several subcells (multi-junction cell) [11][12][13][14]. In this work, cells of the latter approach are investigated, namely, vertically interconnected dual-junction cells realized by monolithic growth of two subcells on top of each other.…”

“…[14]. Other devices where a similar temperature dependence influences the series connection are multi-junction cells designed for the solar spectrum where "2n" junctions are realized with only "n" bandgap materials in order to boost the voltage and reduce the current [15].…”

Conversion efficiencies of single-junction III–V solar cells based on InGaP, GaAs, InGaAsP, and InGaAs for laser wireless power transmission

“…The highest efficiency yet reported at short wavelengths is 66.5% in the case of GaAs multi-junction photo transducers. 1,2) This value, however, was obtained over a relatively short distance of less than 20 mm using an optical fiber laser beam with a wavelength of 841 nm. In a longer wavelength range, an InGaAs single-junction solar cell exhibited a 44.6% efficiency at a relatively low power of 25 mW in response to 1550 nm laser irradiation.…”