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A special issue of Nanomaterials (ISSN 2079-4991).

Deadline for manuscript submissions: closed (31 March 2016) | Viewed by 115043

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Prof. Dr. Guanying Chen

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Guest Editor

School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, China
Interests: lanthanide; crystals and nanocrystals; nonlinear; biophotonics; solar cells
Special Issues, Collections and Topics in MDPI journals

Dr. Zhijun Ning

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Guest Editor

School of Physical Science and Technology, ShanghaiTech University, Shanghai 200031, China

Prof. Dr. Hans Agren

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Division of Theoretical Chemistry and Biology, School of Biology, Royal Institute of Technology, SE-10609 Stocholm, Sweden
Interests: theorectial chemistry; quantum-classical modelling; light-matter interaction; spectroscopy; nanobiotechnology; plasmonic and upconverting nanoparticles

Special Issue Information

Dear Colleagues,

Solar cells are generally regarded as a promising renewable energy source. Though significant progress has been made in recent decades, a complete replacement of traditional energy sources by solar cells still requires improvement in device performance. Recently, the emerging use of nanostructures by newly developed nanotechnology provides opportunities to significantly enhance the efficiency by plasmonic enhancement, reflection enhancement, light scattering, and enhanced carriers collection efficiency, among other attributes. On the other hand, numerous kinds of solar cells, such as perovskite solar cells, colloidal quantum dot solar cells, organic heterojunction solar cells, dye sensitized solar cells have been developed. The combination of solution processed solar cells and nanostructures, leads to a much improved performance of devices. One reason for this is that nanostructures enable significantly enhanced light harvesting in the near infrared or infrared region, where most active materials have poor light absorption capacity. Additionally, the use of nanostructures can lead to enhanced carriers collection efficiency and photocurrent generation.

This Special Issue will present comprehensive research outlining progress on the application of nanostructures to improve the performance of solar cells. This includes the utilization of plasmonic, light reflection or light scattering enhancement to improve light absorption and the construction of new kinds of device structures to improve carriers’ collection. We invite authors to contribute original research articles and review articles covering the current progress on nanostructured solar cells. Potential topics include, but are not limited to:

1. Colloidal quantum dot solar cells based on nanostructured devices.

2. Dyes or colloidal quantum dot sensitized solar cells based on nanostructured electrodes.

3. Perovskite solar cells based on nanostructures.

4. Organic polymer heterojunction solar cells by plasmonic enhancement.

5. Small molecular heterojunction solar cells with nanostructures.

6. Thin film solar cells including amorphous silicon, copper indium gallium selenide solar cells (CuInGaSe), cadmium telluride solar cells based on nanostructures.

7. Nanostructured crystalline silicon solar cells.

Prof. Dr. Guanying Chen
Dr. Zhijun Ning
Prof. Dr. Hans Agren
Guest Editors

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Keywords

Photovolatics
solar cells
nanomaterials
nanostructures
light harvesting
light management
plasmonic
interface engineering
carrier multiplication

Published Papers (14 papers)

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Editorial

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148 KiB

Open AccessEditorial

Nanostructured Solar Cells

by Guanying Chen, Zhijun Ning and Hans Ågren

Nanomaterials 2016, 6(8), 145; https://doi.org/10.3390/nano6080145 - 09 Aug 2016

Cited by 10 | Viewed by 5657

Abstract

We are glad to announce the Special Issue “Nanostructured Solar Cells”, published in Nanomaterials. This issue consists of eight articles, two communications, and one review paper, covering major important aspects of nanostructured solar cells of varying types. From fundamental physicochemical investigations to technological advances, and from single junction solar cells (silicon solar cell, dye sensitized solar cell, quantum dots sensitized solar cell, and small molecule organic solar cell) to tandem multi-junction solar cells, all aspects are included and discussed in this issue to advance the use of nanotechnology to improve the performance of solar cells with reduced fabrication costs. Full article

(This article belongs to the Special Issue Nanostructured Solar Cells)

Research

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3966 KiB

Open AccessArticle

Nano-Photonic Structures for Light Trapping in Ultra-Thin Crystalline Silicon Solar Cells

by Prathap Pathi, Akshit Peer and Rana Biswas

Nanomaterials 2017, 7(1), 17; https://doi.org/10.3390/nano7010017 - 13 Jan 2017

Cited by 45 | Viewed by 9778

Abstract

Thick wafer-silicon is the dominant solar cell technology. It is of great interest to develop ultra-thin solar cells that can reduce materials usage, but still achieve acceptable performance and high solar absorption. Accordingly, we developed a highly absorbing ultra-thin crystalline Si based solar cell architecture using periodically patterned front and rear dielectric nanocone arrays which provide enhanced light trapping. The rear nanocones are embedded in a silver back reflector. In contrast to previous approaches, we utilize dielectric photonic crystals with a completely flat silicon absorber layer, providing expected high electronic quality and low carrier recombination. This architecture creates a dense mesh of wave-guided modes at near-infrared wavelengths in the absorber layer, generating enhanced absorption. For thin silicon (<2 μm) and 750 nm pitch arrays, scattering matrix simulations predict enhancements exceeding 90%. Absorption approaches the Lambertian limit at small thicknesses (<10 μm) and is slightly lower (by ~5%) at wafer-scale thicknesses. Parasitic losses are ~25% for ultra-thin (2 μm) silicon and just 1%–2% for thicker (>100 μm) cells. There is potential for 20 μm thick cells to provide 30 mA/cm² photo-current and >20% efficiency. This architecture has great promise for ultra-thin silicon solar panels with reduced material utilization and enhanced light-trapping. Full article

(This article belongs to the Special Issue Nanostructured Solar Cells)

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2202 KiB

Open AccessCommunication

Ag Nanoparticle–Functionalized Open-Ended Freestanding TiO₂ Nanotube Arrays with a Scattering Layer for Improved Energy Conversion Efficiency in Dye-Sensitized Solar Cells

by Won-Yeop Rho, Myeung-Hwan Chun, Ho-Sub Kim, Hyung-Mo Kim, Jung Sang Suh and Bong-Hyun Jun

Nanomaterials 2016, 6(6), 117; https://doi.org/10.3390/nano6060117 - 15 Jun 2016

Cited by 25 | Viewed by 6833

Abstract

Dye-sensitized solar cells (DSSCs) were fabricated using open-ended freestanding TiO₂ nanotube arrays functionalized with Ag nanoparticles (NPs) in the channel to create a plasmonic effect, and then coated with large TiO₂ NPs to create a scattering effect in order to improve energy conversion efficiency. Compared to closed-ended freestanding TiO₂ nanotube array–based DSSCs without Ag or large TiO₂ NPs, the energy conversion efficiency of closed-ended DSSCs improved by 9.21% (actual efficiency, from 5.86% to 6.40%) with Ag NPs, 6.48% (actual efficiency, from 5.86% to 6.24%) with TiO₂ NPs, and 14.50% (actual efficiency, from 5.86% to 6.71%) with both Ag NPs and TiO₂ NPs. By introducing Ag NPs and/or large TiO₂ NPs to open-ended freestanding TiO₂ nanotube array–based DSSCs, the energy conversion efficiency was improved by 9.15% (actual efficiency, from 6.12% to 6.68%) with Ag NPs and 8.17% (actual efficiency, from 6.12% to 6.62%) with TiO₂ NPs, and by 15.20% (actual efficiency, from 6.12% to 7.05%) with both Ag NPs and TiO₂ NPs. Moreover, compared to closed-ended freestanding TiO₂ nanotube arrays, the energy conversion efficiency of open-ended freestanding TiO₂ nanotube arrays increased from 6.71% to 7.05%. We demonstrate that each component—Ag NPs, TiO₂ NPs, and open-ended freestanding TiO₂ nanotube arrays—enhanced the energy conversion efficiency, and the use of a combination of all components in DSSCs resulted in the highest energy conversion efficiency. Full article

(This article belongs to the Special Issue Nanostructured Solar Cells)

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3935 KiB

Open AccessFeature PaperArticle

Correlation between CdSe QD Synthesis, Post-Synthetic Treatment, and BHJ Hybrid Solar Cell Performance

by Michael Eck and Michael Krueger

Nanomaterials 2016, 6(6), 115; https://doi.org/10.3390/nano6060115 - 14 Jun 2016

Cited by 8 | Viewed by 4556

Abstract

In this publication we show that the procedure to synthesize nanocrystals and the post-synthetic nanocrystal ligand sphere treatment have a great influence not only on the immediate performance of hybrid bulk heterojunction solar cells, but also on their thermal, long-term, and air stability. We herein demonstrate this for the particular case of spherical CdSe nanocrystals, post-synthetically treated with a hexanoic acid based treatment. We observe an influence from the duration of this post-synthetic treatment on the nanocrystal ligand sphere size, and also on the solar cell performance. By tuning the post-synthetic treatment to a certain degree, optimal device performance can be achieved. Moreover, we show how to effectively adapt the post-synthetic nanocrystal treatment protocol to different nanocrystal synthesis batches, hence increasing the reproducibility of hybrid nanocrystal:polymer bulk-heterojunction solar cells, which usually suffers due to the fluctuations in nanocrystal quality of different synthesis batches and synthesis procedures. Full article

(This article belongs to the Special Issue Nanostructured Solar Cells)

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2535 KiB

Open AccessArticle

Enhancing the Photocurrent of Top-Cell by Ellipsoidal Silver Nanoparticles: Towards Current-Matched GaInP/GaInAs/Ge Triple-Junction Solar Cells

by Yiming Bai, Lingling Yan, Jun Wang, Lin Su, Zhigang Yin, Nuofu Chen and Yuanyuan Liu

Nanomaterials 2016, 6(6), 98; https://doi.org/10.3390/nano6060098 - 25 May 2016

Cited by 7 | Viewed by 5094

Abstract

A way to increase the photocurrent of top-cell is crucial for current-matched and highly-efficient GaInP/GaInAs/Ge triple-junction solar cells. Herein, we demonstrate that ellipsoidal silver nanoparticles (Ag NPs) with better extinction performance and lower fabrication temperature can enhance the light harvest of GaInP/GaInAs/Ge solar cells compared with that of spherical Ag NPs. In this method, appropriate thermal treatment parameters for Ag NPs without inducing the dopant diffusion of the tunnel-junction plays a decisive role. Our experimental and theoretical results confirm the ellipsoidal Ag NPs annealed at 350 °C show a better extinction performance than the spherical Ag NPs annealed at 400 °C. The photovoltaic conversion efficiency of the device with ellipsoidal Ag NPs reaches 31.02%, with a nearly 5% relative improvement in comparison with the device without Ag NPs (29.54%). This function of plasmonic NPs has the potential to solve the conflict of sufficient light absorption and efficient carrier collection in GaInP top-cell devices. Full article

(This article belongs to the Special Issue Nanostructured Solar Cells)

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3335 KiB

Open AccessFeature PaperArticle

Improving the Photocurrent in Quantum-Dot-Sensitized Solar Cells by Employing Alloy Pb_xCd_1−xS Quantum Dots as Photosensitizers

by Chunze Yuan, Lin Li, Jing Huang, Zhijun Ning, Licheng Sun and Hans Ågren

Nanomaterials 2016, 6(6), 97; https://doi.org/10.3390/nano6060097 - 25 May 2016

Cited by 25 | Viewed by 6988

Abstract

Ternary alloy Pb_xCd_1−xS quantum dots (QDs) were explored as photosensitizers for quantum-dot-sensitized solar cells (QDSCs). Alloy Pb_xCd_1−xS QDs (Pb_0.54Cd_0.46S, Pb_0.31Cd_0.69S, and Pb_0.24Cd_0.76S) were found to substantially improve the photocurrent of the solar cells compared to the single CdS or PbS QDs. Moreover, it was found that the photocurrent increases and the photovoltage decreases when the ratio of Pb in Pb_xCd_1−xS is increased. Without surface protecting layer deposition, the highest short-circuit current density reaches 20 mA/cm² under simulated AM 1.5 illumination (100 mW/cm²). After an additional CdS coating layer was deposited onto the Pb_xCd_1−xS electrode, the photovoltaic performance further improved, with a photocurrent of 22.6 mA/cm² and an efficiency of 3.2%. Full article

(This article belongs to the Special Issue Nanostructured Solar Cells)

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4151 KiB

Open AccessArticle

Ultraviolet Plasmonic Aluminium Nanoparticles for Highly Efficient Light Incoupling on Silicon Solar Cells

by Yinan Zhang, Boyuan Cai and Baohua Jia

Nanomaterials 2016, 6(6), 95; https://doi.org/10.3390/nano6060095 - 24 May 2016

Cited by 44 | Viewed by 7266

Abstract

Plasmonic metal nanoparticles supporting localized surface plasmon resonances have attracted a great deal of interest in boosting the light absorption in solar cells. Among the various plasmonic materials, the aluminium nanoparticles recently have become a rising star due to their unique ultraviolet plasmonic resonances, low cost, earth-abundance and high compatibility with the complementary metal-oxide semiconductor (CMOS) manufacturing process. Here, we report some key factors that determine the light incoupling of aluminium nanoparticles located on the front side of silicon solar cells. We first numerically study the scattering and absorption properties of the aluminium nanoparticles and the influence of the nanoparticle shape, size, surface coverage and the spacing layer on the light incoupling using the finite difference time domain method. Then, we experimentally integrate 100-nm aluminium nanoparticles on the front side of silicon solar cells with varying silicon nitride thicknesses. This study provides the fundamental insights for designing aluminium nanoparticle-based light trapping on solar cells. Full article

(This article belongs to the Special Issue Nanostructured Solar Cells)

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4375 KiB

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The Influence of Fluorination on Nano-Scale Phase Separation and Photovoltaic Performance of Small Molecular/PC₇₁BM Blends

by Zhen Lu, Wen Liu, Jingjing Li, Tao Fang, Wanning Li, Jicheng Zhang, Feng Feng and Wenhua Li

Nanomaterials 2016, 6(4), 80; https://doi.org/10.3390/nano6040080 - 21 Apr 2016

Cited by 4 | Viewed by 5683

Abstract

To investigate the fluorination influence on the photovoltaic performance of small molecular based organic solar cells (OSCs), six small molecules based on 2,1,3-benzothiadiazole (BT), and diketopyrrolopyrrole (DPP) as core and fluorinated phenyl (DFP) and triphenyl amine (TPA) as different terminal units (DFP-BT-DFP, DFP-BT-TPA, TPA-BT-TPA, DFP-DPP-DFP, DFP-DPP-TPA, and TPA-DPP-TPA) were synthesized. With one or two fluorinated phenyl as the end group(s), HOMO level of BT and DPP based small molecular donors were gradually decreased, inducing high open circuit voltage for fluorinated phenyl based OSCs. DFP-BT-TPA and DFP-DPP-TPA based blend films both displayed stronger nano-scale aggregation in comparison to TPA-BT-TPA and TPA-DPP-TPA, respectively, which would also lead to higher hole motilities in devices. Ultimately, improved power conversion efficiency (PCE) of 2.17% and 1.22% was acquired for DFP-BT-TPA and DFP-DPP-TPA based devices, respectively. These results demonstrated that the nano-scale aggregation size of small molecules in photovoltaic devices could be significantly enhanced by introducing a fluorine atom at the donor unit of small molecules, which will provide understanding about the relationship of chemical structure and nano-scale phase separation in OSCs. Full article

(This article belongs to the Special Issue Nanostructured Solar Cells)

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2523 KiB

Open AccessCommunication

Morphology-Controlled High-Efficiency Small Molecule Organic Solar Cells without Additive Solvent Treatment

by Il Ku Kim, Jun Hyung Jo and Jung-Ho Yun

Nanomaterials 2016, 6(4), 64; https://doi.org/10.3390/nano6040064 - 08 Apr 2016

Cited by 10 | Viewed by 6818

Abstract

This paper focuses on nano-morphology-controlled small-molecule organic solar cells without solvent treatment for high power-conversion efficiencies (PCEs). The maximum high PCE reaches up to 7.22% with a bulk-heterojunction (BHJ) thickness of 320 nm. This high efficiency was obtained by eliminating solvent additives such as 1,8-diiodooctane (DIO) to find an alternative way to control the domain sizes in the BHJ layer. Furthermore, the generalized transfer matrix method (GTMM) analysis has been applied to confirm the effects of applying a different thickness of BHJs for organic solar cells from 100 to 320 nm, respectively. Finally, the study showed an alternative way to achieve high PCE organic solar cells without additive solvent treatments to control the morphology of the bulk-heterojunction. Full article

(This article belongs to the Special Issue Nanostructured Solar Cells)

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2042 KiB

Open AccessArticle

Numerical Study of Complementary Nanostructures for Light Trapping in Colloidal Quantum Dot Solar Cells

by Jue Wei, Qiuyang Xiong, Seyed Milad Mahpeykar and Xihua Wang

Nanomaterials 2016, 6(4), 55; https://doi.org/10.3390/nano6040055 - 25 Mar 2016

Cited by 10 | Viewed by 6578

Abstract

We have investigated two complementary nanostructures, nanocavity and nanopillar arrays, for light absorption enhancement in depleted heterojunction colloidal quantum dot (CQD) solar cells. A facile complementary fabrication process is demonstrated for patterning these nanostructures over the large area required for light trapping in photovoltaic devices. The simulation results show that both proposed periodic nanostructures can effectively increase the light absorption in CQD layer of the solar cell throughout the near-infrared region where CQD solar cells typically exhibit weak light absorption. The complementary fabrication process for implementation of these nanostructures can pave the way for large-area, inexpensive light trapping implementation in nanostructured solar cells. Full article

(This article belongs to the Special Issue Nanostructured Solar Cells)

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2610 KiB

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Investigating the Effect of Carbon Nanotube Diameter and Wall Number in Carbon Nanotube/Silicon Heterojunction Solar Cells

by Tom Grace, LePing Yu, Christopher Gibson, Daniel Tune, Huda Alturaif, Zeid Al Othman and Joseph Shapter

Nanomaterials 2016, 6(3), 52; https://doi.org/10.3390/nano6030052 - 22 Mar 2016

Cited by 37 | Viewed by 7538

Abstract

Suspensions of single-walled, double-walled and multi-walled carbon nanotubes (CNTs) were generated in the same solvent at similar concentrations. Films were fabricated from these suspensions and used in carbon nanotube/silicon heterojunction solar cells and their properties were compared with reference to the number of walls in the nanotube samples. It was found that single-walled nanotubes generally produced more favorable results; however, the double and multi-walled nanotube films used in this study yielded cells with higher open circuit voltages. It was also determined that post fabrication treatments applied to the nanotube films have a lesser effect on multi-walled nanotubes than on the other two types. Full article

(This article belongs to the Special Issue Nanostructured Solar Cells)

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2760 KiB

Open AccessFeature PaperArticle

Influence of Nitrogen Doping on Device Operation for TiO₂-Based Solid-State Dye-Sensitized Solar Cells: Photo-Physics from Materials to Devices

by Jin Wang, Kosti Tapio, Aurélie Habert, Sebastien Sorgues, Christophe Colbeau-Justin, Bernard Ratier, Monica Scarisoreanu, Jussi Toppari, Nathalie Herlin-Boime and Johann Bouclé

Nanomaterials 2016, 6(3), 35; https://doi.org/10.3390/nano6030035 - 23 Feb 2016

Cited by 19 | Viewed by 7399

Abstract

Solid-state dye-sensitized solar cells (ssDSSC) constitute a major approach to photovoltaic energy conversion with efficiencies over 8% reported thanks to the rational design of efficient porous metal oxide electrodes, organic chromophores, and hole transporters. Among the various strategies used to push the performance ahead, doping of the nanocrystalline titanium dioxide (TiO₂) electrode is regularly proposed to extend the photo-activity of the materials into the visible range. However, although various beneficial effects for device performance have been observed in the literature, they remain strongly dependent on the method used for the production of the metal oxide, and the influence of nitrogen atoms on charge kinetics remains unclear. To shed light on this open question, we synthesized a set of N-doped TiO₂ nanopowders with various nitrogen contents, and exploited them for the fabrication of ssDSSC. Particularly, we carefully analyzed the localization of the dopants using X-ray photo-electron spectroscopy (XPS) and monitored their influence on the photo-induced charge kinetics probed both at the material and device levels. We demonstrate a strong correlation between the kinetics of photo-induced charge carriers probed both at the level of the nanopowders and at the level of working solar cells, illustrating a direct transposition of the photo-physic properties from materials to devices. Full article

(This article belongs to the Special Issue Nanostructured Solar Cells)

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Review

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3245 KiB

Open AccessReview

Graphene and Carbon Quantum Dot-Based Materials in Photovoltaic Devices: From Synthesis to Applications

by Sofia Paulo, Emilio Palomares and Eugenia Martinez-Ferrero

Nanomaterials 2016, 6(9), 157; https://doi.org/10.3390/nano6090157 - 25 Aug 2016

Cited by 122 | Viewed by 16536

Abstract

Graphene and carbon quantum dots have extraordinary optical and electrical features because of their quantum confinement properties. This makes them attractive materials for applications in photovoltaic devices (PV). Their versatility has led to their being used as light harvesting materials or selective contacts, either for holes or electrons, in silicon quantum dot, polymer or dye-sensitized solar cells. In this review, we summarize the most common uses of both types of semiconducting materials and highlight the significant advances made in recent years due to the influence that synthetic materials have on final performance. Full article

(This article belongs to the Special Issue Nanostructured Solar Cells)

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3293 KiB

Open AccessReview

Enhancing Solar Cell Efficiency Using Photon Upconversion Materials

by Yunfei Shang, Shuwei Hao, Chunhui Yang and Guanying Chen

Nanomaterials 2015, 5(4), 1782-1809; https://doi.org/10.3390/nano5041782 - 27 Oct 2015

Cited by 148 | Viewed by 14791

Abstract

Photovoltaic cells are able to convert sunlight into electricity, providing enough of the most abundant and cleanest energy to cover our energy needs. However, the efficiency of current photovoltaics is significantly impeded by the transmission loss of sub-band-gap photons. Photon upconversion is a promising route to circumvent this problem by converting these transmitted sub-band-gap photons into above-band-gap light, where solar cells typically have high quantum efficiency. Here, we summarize recent progress on varying types of efficient upconversion materials as well as their outstanding uses in a series of solar cells, including silicon solar cells (crystalline and amorphous), gallium arsenide (GaAs) solar cells, dye-sensitized solar cells, and other types of solar cells. The challenge and prospect of upconversion materials for photovoltaic applications are also discussed Full article

(This article belongs to the Special Issue Nanostructured Solar Cells)

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