Radiation Effects in Thinned GaAs Photovoltaics Incorporating DBRs for Improved Radiation Tolerance of Multijunctions

Polly, Stephen J.; Nelson, George T.; D'Rozario, Julia R.; Tatavarti, Rao; Hubbard, Seth M.

doi:10.1109/pvsc40753.2019.8980875

Cited by 6 publications

(6 citation statements)

References 4 publications

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“…However, increasing the absorbed light is more challenging for multi-junction than for single junction cells; the optical structure has to be placed behind the junction which absorbs the least light, otherwise the subsequent junctions-having a lower bandgap-will absorb the incoming photons. This problem has restricted the strategies for compensating the thinning of the middle junction to using distributed Bragg reflectors (DBRs) between the middle and the bottom subcells [4,8,14]. These reflective elements are employed in conjunction with a front surface antireflective coating (ARC).…”

Section: Introductionmentioning

confidence: 99%

Light absorption enhancement and radiation hardening for triple junction solar cell through bioinspired nanostructures

et al. 2021

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Multi-junction solar cells constitute the main source of power for space applications. However, exposure of solar cells to the space radiation environment significantly degrades their performance across the mission lifetime. Here, we seek to improve the radiation hardness of the triple junction solar cell, GaInP/Ga(In)As/Ge, by decreasing the thickness of the more sensitive middle junction. Thin junctions facilitate the collection of minority carriers and show slower degradation due to defects. However, thinning the junction decreases the absorption, and consequently, the expected photocurrent. To compensate for this loss, we examined two bioinspired surface patterns that exhibit anti-reflective and light-trapping properties: (a) the moth-eye structure which enables vision in poorly illuminated environments and (b) the patterns of the hard cell of a unicellular photosynthetic micro-alga, the diatoms. We parametrize and optimize the biomimetic structures, aiming to maximize the absorbed light by the solar cell while achieving significant reduction in the middle junction thickness. The density of the radiation-induced defects is independent of the junction thickness, as we demonstrate using Monte Carlo simulations, allowing the direct comparison of different combinations of middle junction thicknesses and light trapping structures. We incorporate the radiation effects into the solar cell model as a decrease in minority carrier lifetime and an increase in surface recombination velocity, and we quantify the gain in efficiency for different combinations of junction thickness and the light-trapping structure at equal radiation damage. Solar cells with thin junctions compensated by the light-trapping structures offer a promising approach to improve solar cell radiation hardness and robustness, with up to 2% higher end-of-life efficiency than the commonly used configuration at high radiation exposure.

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Section: Introductionmentioning

confidence: 99%

Light absorption enhancement and radiation hardening for triple junction solar cell through bioinspired nanostructures

et al. 2021

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show abstract

Section: Introductionmentioning

confidence: 99%

“…Lowering the thickness can also offer better performance in cells that are grown in ways that do not necessarily ensure high crystalline quality, such as hydride vapor phase epitaxy (HVPE) 1,2 or III-V on silicon (III-V/Si), 3 which both have the potential to reduce costs of III-V cells even further. Ultrathin cells are also less affected by proton and electron radiation induced defects [4][5][6] and can potentially achieve a higher open-circuit voltage (V OC ) than thicker structures. 7 With a suitable light-trapping scheme increasing the path length through the solar cell, the ultrathin structures can be made optically thick and achieve current-densities matching those of conventional thin film (2-3 μm) GaAs cells.…”

Section: Introductionmentioning

confidence: 99%

Ultrathin GaAs solar cells with a high surface roughness GaP layer for light‐trapping application

Woude

Krabben

Bauhuis

et al. 2022

Progress in Photovoltaics

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By reducing the thickness of the absorber layers, ultrathin GaAs solar cells can be fabricated in a more cost-effective manner using less source material and shorter deposition times. In this work, ultrathin GaAs solar cells are presented with a diffuse scattering layer based on wide bandgap GaP grown directly on the device layers of the cells with MOCVD. The roughness and surface morphology are quantified using atomic force microscopy and the resulting diffuse scattering capability is assessed using wavelength-dependent reflectance measurements. Ohmic rear contacts are made using contact points etched through the GaP layer, for which an etching procedure using I 2 :KI was developed and optimized. The performance of the GaP textured ultrathin GaAs cells are compared with equivalent planar cells using current densityvoltage measurements and external quantum efficiency measurements, where the GaP textured cells demonstrate an increase of 6.7% in the short-circuit current density (J SC ), which was found to be as high as 21.9 mAÁcm À2 as a result of increased photon absorption by light-trapping.

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“…While, distributed Bragg reflectors (DBR) can be introduced into thin film solar cell to improve EQE when the MCDL is not long enough. [18][19][20][21] The main reason for this is that incident photons with a specific wavelength range can be absorbed twice by the base layer when DBR structure is placed under the back side of solar cell, and the material thickness can be designed thinner than that without DBR. Therefore, DBR is very suitable for GaInNAs solar cell due to the shorter MCDL, especially as it is prepared by MOVPE technology.…”

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confidence: 99%

High current of GaInNAs solar cell integrating distributed Bragg reflectors grown by metalorganic vapor phase epitaxy

Zhang¹,

Yang²,

Li³

et al. 2021

Appl. Phys. Express

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GaInNAs junctions can be applied to the lattice-matched five-junction (5J) or six-junction (6J) solar cells to achieve ultra-high efficiency. In this work, a GaInNAs solar cell integrating distributed Bragg reflectors (DBR) is grown by metalorganic vapor phase epitaxy. According to external quantum efficiency measurements, the photocurrent can be improved by ∼20% due to DBR. Meanwhile, a short-circuit current (J sc ) of GaInNAs DBR-cell is obtained high as 13.78 mA cm −2 under the air mass (AM0) spectrum, which is completely satisfied the demand of 36%-efficiency 5J solar cell (∼ 12 mA cm −2 ). Finally, Dark-IV characteristics reveal that the introduction of DBR does not deteriorate GaInNAs quality.

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Radiation Effects in Thinned GaAs Photovoltaics Incorporating DBRs for Improved Radiation Tolerance of Multijunctions

Cited by 6 publications

References 4 publications

Light absorption enhancement and radiation hardening for triple junction solar cell through bioinspired nanostructures

Light absorption enhancement and radiation hardening for triple junction solar cell through bioinspired nanostructures

Ultrathin GaAs solar cells with a high surface roughness GaP layer for light‐trapping application

High current of GaInNAs solar cell integrating distributed Bragg reflectors grown by metalorganic vapor phase epitaxy

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