Fabrication and analysis of multijunction solar cells with a quantum dot (In)GaAs junction

Kerestes, Christopher; Polly, Stephen J.; Forbes, David V.; Bailey, Christopher G.; Podell, Adam; Spann, John; Patel, Pravin; Richards, B. C.; Sharps, Paul; Hubbard, Seth M.

doi:10.1002/pip.2378

Cited by 35 publications

(23 citation statements)

References 23 publications

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“…Then, we substituted parameters ε B and n B with their values obtained as functions of bias voltage V and concentration X in Equations (6), (7), and (14). Such substitution yielded also the quasi-Fermi levels μ Q and μ C and the photocurrent J B as functions of bias voltage V and sunlight concentration X.…”

Section: Calculation Of Parameters and Currentsmentioning

confidence: 99%

Impact of spatial separation of type‐II GaSb quantum dots from the depletion region on the conversion efficiency limit of GaAs solar cells

Kechiantz

Afanasev

Lazzari

2014

Progress in Photovoltaics

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The purpose of this work is to look for a practical structure for application of quantum dots (QD) in solar cells in order to enhance sub-band gap photon absorption. We focuse on a stack of strain-compensated GaSb/GaAs type-II QDs. We propose a novel structure with GaSb/GaAs type-II QD absorber embedded in the p-doped region of ideal solar cell, but spatially separated from the depletion region. We developed the model and used the detailed balance principle along with Poisson and continuity equations for calculating of the energy band bending along with the photocurrent and the dark current, and the conversion efficiency of the cell. Our model takes into account both single-photon and double-photon absorption as well as non-radiative processes in QDs and predicts that oncentration from 1-sun to 500-sun raises the efficiency from 30% to 50%. We showed that accumulation of charge in the QD absorber is the clue to understanding of potentially superior performance of the proposed solar cell. An attractive feature of the proposed solar cell is that QDs do not reduce the open circuit voltage but facilitate generation of the additional photocurrent to the extent that photovoltaic characteristics reduce to that of ideal IB solar cell while the efficiency meets the Luque-Marti limit. It should be noted that, although non-radiative processes like relaxation in QDs and recombination through QDs degrade photovoltaic characteristics of the proposed solar cell, its conversion efficiency is still predicted to be above the Shockley-Queisser limit by 5% to 10%. This study is an important step toward producing practical solar cells that benefit from additional photocurrent generated by sub-band gap photons.

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Section: Calculation Of Parameters and Currentsmentioning

confidence: 99%

Impact of spatial separation of type‐II GaSb quantum dots from the depletion region on the conversion efficiency limit of GaAs solar cells

Kechiantz

Afanasev

Lazzari

2014

Progress in Photovoltaics

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“…3.1. X-ray diffraction and photoluminescence characterization of InGaAs/GaAs QD structure [15][16][17][18][19][20][21] The epitaxy quality of cells with and without layers of QDs was examined by DC-XRD measurement, as shown in Figure 2. Satellite peaks originating from the InGaAs/GaAs QD structure were clearly observed in the XRD curves.…”

Section: Resultsmentioning

confidence: 99%

“…In summary, the cell with the proposed layer of QDs in the middle cell demonstrated a 1.0% absolute gain in efficiency compared with the reference cell. [16,20,21] these cells must have very low reflectance at wavelengths of 665-885 nm. EQE values beyond 90% were achieved at wavelengths of 450-630 nm in the top cell and 700-870 nm in the middle cell of both types of device.…”

Section: Resultsmentioning

confidence: 99%

Optical and electrical characteristics of high‐efficiency InGaP/InGaAs/Ge triple‐junction solar cell incorporated with InGaAs/GaAs QD layers in the middle cell

Lee

Yang

et al. 2015

Progress in Photovoltaics

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This study presents high efficiency InGaP/InGaAs/Ge triple-junction (3-J) solar cells incorporated in the middle cell with layers of InGaAs/GaAs quantum dots (QDs) grown by metal organic chemical vapor deposition to achieve 33.5% conversion efficiency (η) under one-sun AM 1.5 G illumination. We investigated the epitaxial structure and optical and electrical properties of InGaP/InGaAs/Ge 3-J solar cells with and without layers of QDs. We then measured X-ray diffraction (XRD), photoluminescence (PL), optical reflectance, dark and photovoltaic current-voltage (I-V) characteristics, external quantum efficiency (EQE) response, and capacitance-voltage (C-V) as a function of frequency under dark and illuminated conditions at room temperature. The use of 50 pairs of In 0.7 Ga 0.3 As (QD)/GaAs (Barrier) QD structure produced an impressive 35% enhancement in EQE at wavelengths of 900-930 nm. This resulted in a short-circuit current density of 15.43 mA/cm 2 , an open-circuit voltage of 2.54 V, a fill factor of 84.7%, and a η of 33.5%. The 3-J cell with the proposed layers of QDs also demonstrated a 1.0% absolute gain in efficiency compared with a reference cell without QDs. Our XRD, PL, and C-V results revealed that highly stacked InGaAs/GaAs QD layers of high quality can be grown with very little degradation in crystal quality and without the need for strain compensation techniques.

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“…Nanostructured absorbers based on quantum-dots (QD) provide tunable sub-bandgap transitions to enhance the infrared photoresponse of single-junction solar cells [1] and to improve current matching in multijunction cells [2,3]. Also, they offer a promising path towards the development of novel photovoltaics concepts, beyond the Shockley-Queisser (SQ) limit, such as the intermediate band (IB) solar cell [4,5].…”

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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Fabrication and analysis of multijunction solar cells with a quantum dot (In)GaAs junction

Cited by 35 publications

References 23 publications

Impact of spatial separation of type‐II GaSb quantum dots from the depletion region on the conversion efficiency limit of GaAs solar cells

Impact of spatial separation of type‐II GaSb quantum dots from the depletion region on the conversion efficiency limit of GaAs solar cells

Optical and electrical characteristics of high‐efficiency InGaP/InGaAs/Ge triple‐junction solar cell incorporated with InGaAs/GaAs QD layers in the middle cell

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

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