Inverted growth evaluation for epitaxial lift off (ELO) quantum dot solar cell and enhanced absorption by back surface texturing

Smith, Brittany L.; Slocum, Michael A.; Bittner, Zachary S.; Dai, Yushuai; Nelson, George T.; Hellstroem, Staffan; Tatavarti, Rao; Hubbard, Seth M.

doi:10.1109/pvsc.2016.7749820

Cited by 13 publications

(9 citation statements)

References 11 publications

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“…For III‐V solar cells however, light‐trapping schemes based on simple wet etches that directly texture the semiconductor surface have not been reported. Typical strategies to incorporate light trapping in III‐V cells employ plasmonic scatterers, nanostructured window layers, and (dielectric) nanostructures at the rear or periodic gratings for (multi)resonant absorption . Despite the success of these methods in increasing the absorptance, they can typically be experimentally challenging, difficult to upscale or introduce substantial parasitic optical or electrical losses into the cells.…”

Section: Introductionmentioning

confidence: 99%

A facile light‐trapping approach for ultrathin GaAs solar cells using wet chemical etching

Eerden¹,

Bauhuis²,

Mulder³

et al. 2019

Progress in Photovoltaics

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Thinning down the absorber layer of GaAs solar cells can reduce their cost and improve their radiation hardness, which is important for space applications. However, the lighttrapping schemes necessary to achieve high absorptance in these cells can be experimentally challenging or introduce various parasitic losses. In this work, a facile light‐trapping approach based on wet chemical etching is demonstrated. The rear‐side contact layer of ultrathin GaAs solar cells is wet‐chemically textured in between local Ohmic contact points using an NaOH‐based etchant. The resulting contact layer morphology is characterized using atomic force microscopy and scanning electron miscroscopy. High broadband diffuse reflectance and haze factors are measured on bare and Ag‐coated textured contact layers. The textured contact layer is successfully integrated as a diffusive rear mirror in thin‐film solar cells comprising a 300‐nm GaAs absorber and Ag rear contact. Consistent increases in short‐circuit current density (JSC) of approximately 3 mA cm−2 (15%) are achieved in the textured cells, while the open‐circuit voltages and fill factors do not suffer from the textured rear mirror. The best cell achieves a JSC of 24.8 mA cm−2 and a power conversion efficiency of 21.4%. The textured rear mirror enhances outcoupling of luminescence at open circuit, leading to a strong increase in the external luminescent efficiency.

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Section: Introductionmentioning

confidence: 99%

A facile light‐trapping approach for ultrathin GaAs solar cells using wet chemical etching

Eerden¹,

Bauhuis²,

Mulder³

et al. 2019

Progress in Photovoltaics

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“…In high-quality QDSCs operating in the thermally-limited regime, experimental [20,8] and theoretical [22,23] works show that the maximum attainable V oc is linearly correlated with the energy band gap of the QD ground state. V oc approaching 1 V has been demonstrated only in 10× and 40× QD layer cells (with shallow QDs and in-plane density well below 10 11 cm −2 ) by implementing complex strain compensation techniques during the epitaxial growth [24,25,26].…”

Section: Introductionmentioning

confidence: 99%

“…A promising alternative (and even somewhat complementary) path to effectively enhance QD photogeneration is offered by light management schemes that can be implemented within a thin-film solar cell architecture [27,26,28]. Thin-film III-V technologies based on epitaxial lift-off (ELO) [29,30,9] are among the most promising approaches in view of the remarkable reduction of mass and cost (because ELO makes possible wafer reuse), and flexibility.…”

Section: Introductionmentioning

confidence: 99%

Light-trapping enhanced thin-film III-V quantum dot solar cells fabricated by epitaxial lift-off

Cappelluti

Kim

Eerden³

et al. 2018

Solar Energy Materials and Solar Cells

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We report thin-film InAs/GaAs quantum dot (QD) solar cells with n − i − p + deep junction structure and planar back reflector fabricated by epitaxial lift-off (ELO) of full 3-inch wafers. External quantum efficiency measurements demonstrate twofold enhancement of the QD photocurrent in the ELO QD cell compared to the wafer-based QD cell. In the GaAs wavelength range, the ELO QD cell perfectly preserves the current collection efficiency of the baseline single-junction ELO cell. We demonstrate by full-wave optical simulations that integrating a micro-patterned diffraction grating in the ELO cell rearside provides more than tenfold enhancement of the near-infrared light harvesting by QDs. Experimental results are thoroughly discussed with the help of physics-based simulations to single out the impact of QD dynamics and defects on the cell photovoltaic behavior. It is demonstrated that non radiative recombination in the QD stack is the bottleneck for the open circuit voltage (V oc ) of the reported devices. More important, our theoretical calculations demonstrate that the V oc offest of 0.3 V from the QD ground state identified by Tanabe et al., 2012, from a collection of experimental data of high quality III-V QD solar cells is a reliable -albeit conservative -metric to gauge the attainable V oc and to quantify the scope for improvement by reducing non radiative recombination. Provided that material quality issues are solved, we demonstrate -by transport and rigorous electromagnetic simulations -that light-trapping enhanced thin-film cells with twenty InAs/GaAs QD layers reach efficiency higher than 28% under unconcentrated light, ambient temperature. If photon recycling can be fully exploited, 30% efficiency is deemed to be feasible.

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“…To overcome these limitations, QD material engineering [3] and light trapping approaches are required [4]. Diffraction gratings [5][6][7] and plasmonics [8] have been investigated to enhance the near infrared (NIR) absorption of QDs and quantum wells. In [9] we have recently reported QD thin-film cells fabricated by epitaxial lift-off demonstrating a two-fold increase of QD NIR photocurrent [9] through the integration of a planar reflector.…”

Section: Introductionmentioning

confidence: 99%

Guided-mode resonance gratings for enhanced mid-infrared absorption in quantum dot intermediate-band solar cells

Elsehrawy¹,

Niemi²,

Cappelluti³

2018

Opt. Express

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Achieving strong absorption of low-energy photons is one of the key issues to demonstrate quantum dot solar cells working in the intermediate band regime at practical concentration factors and operating temperatures. Guided-mode resonance effects may enable large enhancement of quantum dot intraband optical transitions. We propose quantum dot thin-film cells designed to have significant field waveguiding in the quantum dot stack region and patterned at the rear-side with a sub-wavelength diffraction grating. Remarkable increase of the optical path length at mid-infrared wavelengths is shown owing to guided-mode resonances. Design guidelines are presented for energy and strength of the second-photon absorption for III-V quantum dots, such as InAs/GaAs and GaSb/GaAs, whose intraband and intersubband transitions roughly extends over the 2 - 8 µm range. The proposed design can also be applied to quantum dot infrared detectors. Angle-selectivity is discussed in view of applications in concentrator photovoltaic systems and infrared imaging systems.

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Inverted growth evaluation for epitaxial lift off (ELO) quantum dot solar cell and enhanced absorption by back surface texturing

Cited by 13 publications

References 11 publications

A facile light‐trapping approach for ultrathin GaAs solar cells using wet chemical etching

A facile light‐trapping approach for ultrathin GaAs solar cells using wet chemical etching

Light-trapping enhanced thin-film III-V quantum dot solar cells fabricated by epitaxial lift-off

Guided-mode resonance gratings for enhanced mid-infrared absorption in quantum dot intermediate-band solar cells

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