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  1. Article: Missing Excitons: How Energy Transfer Competes with Free Charge Generation in Dilute-Donor/Acceptor Systems.

    Carr, Joshua M / Gish, Melissa K / Reid, Obadiah G / Rumbles, Garry

    ACS energy letters

    2024  Volume 9, Issue 3, Page(s) 896–907

    Abstract: Energy transfer across the donor-acceptor interface in organic photovoltaics is usually beneficial to device performance, as it assists energy transport to the site of free charge generation. Here, we present a case where the opposite is true: dilute ... ...

    Abstract Energy transfer across the donor-acceptor interface in organic photovoltaics is usually beneficial to device performance, as it assists energy transport to the site of free charge generation. Here, we present a case where the opposite is true: dilute donor molecules in an acceptor host matrix exhibit ultrafast excitation energy transfer (EET) to the host, which suppresses the free charge yield. We observe an optimal photochemical driving force for free charge generation, as detected via time-resolved microwave conductivity (TRMC), but with a low yield when the sensitizer is excited. Meanwhile, transient absorption shows that transferred excitons efficiently produce charge-transfer states. This behavior is well described by a competition for the excited state between long-range electron transfer that produces free charge and EET that ultimately produces only localized charge-transfer states. It cannot be explained if the most localized CT states are the intermediate between excitons and the free charge in this system.
    Language English
    Publishing date 2024-02-08
    Publishing country United States
    Document type Journal Article
    ISSN 2380-8195
    ISSN 2380-8195
    DOI 10.1021/acsenergylett.3c01969
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Charge Concentration Limits the Hydrogen Evolution Rate in Organic Nanoparticle Photocatalysts.

    O'Connor, Max M / Aubry, Taylor J / Reid, Obadiah G / Rumbles, Garry

    Advanced materials (Deerfield Beach, Fla.)

    2023  Volume 36, Issue 20, Page(s) e2210481

    Abstract: Time-resolved microwave conductivity is used to compare aqueous-soluble organic nanoparticle photocatalysts and bulk thin films composed of the same mixture of semiconducting polymer and non-fullerene acceptor molecule and the relationship between ... ...

    Abstract Time-resolved microwave conductivity is used to compare aqueous-soluble organic nanoparticle photocatalysts and bulk thin films composed of the same mixture of semiconducting polymer and non-fullerene acceptor molecule and the relationship between composition, interfacial surface area, charge-carrier dynamics, and photocatalytic activity is examined. The rate of hydrogen evolution reaction by nanoparticles composed of various donor:acceptor blend ratio compositions is quantitatively measured, and it is found that the most active blend ratio displays a hydrogen quantum yield of 0.83% per photon. Moreover, it is found that nanoparticle photocatalytic activity corresponds directly to charge generation, and that nanoparticles have 3× more long-lived accumulated charges relative to bulk samples of the same material composition. These results suggest that, under the current reaction conditions, with ≈3× solar flux, catalytic activity by the nanoparticles is limited by the concentration of electrons and holes in operando and not a finite number of active surface sites or the catalytic rate at the interface. This provides a clear design goal for the next generation of efficient photocatalytic nanoparticles.
    Language English
    Publishing date 2023-07-02
    Publishing country Germany
    Document type Journal Article
    ZDB-ID 1474949-X
    ISSN 1521-4095 ; 0935-9648
    ISSN (online) 1521-4095
    ISSN 0935-9648
    DOI 10.1002/adma.202210481
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  3. Book ; Conference proceedings: Physical chemistry of interfaces and nanomaterials VII

    Rumbles, Garry

    11 - 12 August 2008, San Diego, California, USA

    (Proceedings of SPIE ; 7034)

    2008  

    Event/congress Conference (2008.08.11-12, SanDiegoCalif.)
    Author's details sponsored and publ. by SPIE. Garry Rumbles ..., ed
    Series title Proceedings of SPIE ; 7034
    Keywords Chemistry, Physical and theoretical ; Interfaces (Physical sciences) ; Nanostructured materials ; Surfaces (Physics)
    Language English
    Size Getr. Zählung [ca. 100 S.], Ill., graph. Darst.
    Publisher SPIE
    Publishing place Bellingham, Wash
    Document type Book ; Conference proceedings
    ISBN 9780819472540 ; 0819472549
    Database Library catalogue of the German National Library of Science and Technology (TIB), Hannover

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  4. Article: Resonance Energy Transfer Enables Efficient Planar Heterojunction Organic Solar Cells

    Reid, ObadiahG / Rumbles Garry

    The Journal of Physical Chemistry C. 2016 Jan. 14, v. 120, no. 1

    2016  

    Abstract: Poor energy transport in disordered organic materials is one of the key problems that must be overcome to produce efficient organic solar cells. Usually, this is accomplished by blending the donor and acceptor molecules into a bulk heterojunction. In ... ...

    Abstract Poor energy transport in disordered organic materials is one of the key problems that must be overcome to produce efficient organic solar cells. Usually, this is accomplished by blending the donor and acceptor molecules into a bulk heterojunction. In this article, we investigate an alternative approach to cell design: planar mulitilayer hetrojunctions with efficient energy transport to a central reaction center. We use an experimentally verified Monte Carlo model of energy transport to show that an appropriately engineered planar multilayer stack can achieve power conversion efficiencies comparable to those of the best bulk heterojunction devices. The key to this surprising performance is careful control of the optical properties and thicknesses of each layer to promote Förster resonance energy transfer from antenna/transport layers to a central reaction center. We provide detailed design rules for fabricating efficient planar heterojunction organic cells.
    Keywords Monte Carlo method ; energy transfer ; mixing ; optical properties ; photovoltaic cells ; physical chemistry
    Language English
    Dates of publication 2016-0114
    Size p. 87-97.
    Publishing place American Chemical Society
    Document type Article
    ISSN 1932-7455
    DOI 10.1021%2Facs.jpcc.5b10276
    Database NAL-Catalogue (AGRICOLA)

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  5. Book ; Conference proceedings: Electron transfer in nanomaterials

    Rumbles, Garry

    proceedings of the international symposium ; [Symposium on Charge Transfer Processes in Semi-Conductor and Metal Nanoparticles held at the 205th meeting of the Electrochemical Society in San Antonio, Texas, May 9th - 14th 2004]

    (Proceedings volume / Electrochemical Society ; 2004-22)

    2006  

    Institution Electrochemical Society / Energy Technology Division
    Electrochemical Society / Fullerenes, Nanotubes, and Carbon Nanoclusters Division
    Symposium on Charge Transfer Processes in Semi-Conductor and Metal Nanoparticles
    Event/congress Meeting of the Electrochemical Society (205, 2004.05.09-14, SanAntonioTex.) ; Symposium on Charge Transfer Processes in Semi-Conductor and Metal Nanoparticles (2004.05.09-14, SanAntonioTex.)
    Author's details sponsoring divisions: Fullerenes, Nanotubes, and Carbon Nanostructures, and Energy Technology. Ed.: G. Rumbles
    Series title Proceedings volume / Electrochemical Society ; 2004-22
    Keywords Nanoparticles ; Nanostructured materials
    Language English
    Size VIII, 458 S
    Publisher Electrochemical Society
    Publishing place Pennington, NJ
    Document type Book ; Conference proceedings
    ISBN 1566774357 ; 9781566774352
    Database Library catalogue of the German National Library of Science and Technology (TIB), Hannover

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  6. Article ; Online: Metal-Carbodithioate-Based 3D Semiconducting Metal-Organic Framework: Porous Optoelectronic Material for Energy Conversion.

    Li, Xinlin / Anderson, Ryther / Fry, H Christopher / Pratik, Saied Md / Xu, Wenqian / Goswami, Subhadip / Allen, Taylor G / Yu, Jierui / Rajasree, Sreehari Surendran / Cramer, Christopher J / Rumbles, Garry / Gómez-Gualdrón, Diego A / Deria, Pravas

    ACS applied materials & interfaces

    2023  Volume 15, Issue 23, Page(s) 28228–28239

    Abstract: Solar energy conversion requires the working compositions to generate photoinduced charges with high potential and the ability to deliver charges to the catalytic sites and/or external electrode. These two properties are typically at odds with each other ...

    Abstract Solar energy conversion requires the working compositions to generate photoinduced charges with high potential and the ability to deliver charges to the catalytic sites and/or external electrode. These two properties are typically at odds with each other and call for new molecular materials with sufficient conjugation to improve charge conductivity but not as much conjugation as to overly compromise the optical band gap. In this work, we developed a semiconducting metal-organic framework (MOF) prepared explicitly through metal-carbodithioate "(-CS
    Language English
    Publishing date 2023-05-31
    Publishing country United States
    Document type Journal Article
    ISSN 1944-8252
    ISSN (online) 1944-8252
    DOI 10.1021/acsami.3c04200
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. Article: Beyond n-dopants for organic semiconductors: use of bibenzo[

    Tang, Kan / Brown, Megan R / Risko, Chad / Gish, Melissa K / Rumbles, Garry / Pham, Phuc H / Luca, Oana R / Barlow, Stephen / Marder, Seth R

    Beilstein journal of organic chemistry

    2023  Volume 19, Page(s) 1912–1922

    Abstract: 2,2'-Bis(4-dimethylaminophenyl)- and 2,2'-dicyclohexyl-1,1',3,3'-tetramethyl-2,2',3,3'-tetrahydro-2,2'-bibenzo[ ...

    Abstract 2,2'-Bis(4-dimethylaminophenyl)- and 2,2'-dicyclohexyl-1,1',3,3'-tetramethyl-2,2',3,3'-tetrahydro-2,2'-bibenzo[
    Language English
    Publishing date 2023-12-14
    Publishing country Germany
    Document type Journal Article
    ZDB-ID 2192461-2
    ISSN 1860-5397
    ISSN 1860-5397
    DOI 10.3762/bjoc.19.142
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  8. Article: PCET-Based Ligand Limits Charge Recombination with an Ir(III) Photoredox Catalyst

    Sayre, Hannah / Ripberger, Hunter H. / Odella, Emmanuel / Zieleniewska, Anna / Heredia, Daniel A. / Rumbles, Garry / Scholes, Gregory D. / Moore, Thomas A. / Moore, Ana L. / Knowles, Robert R.

    Journal of the American Chemical Society. 2021 Aug. 11, v. 143, no. 33

    2021  

    Abstract: Upon photoinitiated electron transfer, charge recombination limits the quantum yield of photoredox reactions for which the rates for the forward reaction and back electron transfer are competitive. Taking inspiration from a proton-coupled electron ... ...

    Abstract Upon photoinitiated electron transfer, charge recombination limits the quantum yield of photoredox reactions for which the rates for the forward reaction and back electron transfer are competitive. Taking inspiration from a proton-coupled electron transfer (PCET) process in Photosystem II, a benzimidazole-phenol (BIP) has been covalently attached to the 2,2′-bipyridyl ligand of [Ir(dF(CF₃)ppy)₂(bpy)][PF₆] (dF(CF₃)ppy = 2-(2,4-difluorophenyl)-5-(trifluoromethyl)pyridine; bpy = 2,2′-bipyridyl). Excitation of the [Ir(dF(CF₃)ppy)₂(BIP-bpy)][PF₆] photocatalyst results in intramolecular PCET to form a charge-separated state with oxidized BIP. Subsequent reduction of methyl viologen dication (MV²⁺), a substrate surrogate, by the reducing moiety of the charge separated species demonstrates that the inclusion of BIP significantly slows the charge recombination rate. The effect of ∼24-fold slower charge recombination in a photocatalytic phthalimide ester reduction resulted in a greater than 2-fold increase in reaction quantum efficiency.
    Keywords chemical bonding ; electron transfer ; ligands ; moieties ; oxidation ; paraquat ; photocatalysis ; photocatalysts ; phthalimide ; pyridines
    Language English
    Dates of publication 2021-0811
    Size p. 13034-13043.
    Publishing place American Chemical Society
    Document type Article
    ZDB-ID 3155-0
    ISSN 1520-5126 ; 0002-7863
    ISSN (online) 1520-5126
    ISSN 0002-7863
    DOI 10.1021/jacs.1c01701
    Database NAL-Catalogue (AGRICOLA)

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    In stock of ZB MED Bonn / Germany

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  9. Article: Photoinduced Carrier Generation and Recombination Dynamics of a Trilayer Cascade Heterojunction Composed of Poly(3-hexylthiophene), Titanyl Phthalocyanine, and C60

    Park, Jaehong / Reid Obadiah G / Rumbles Garry

    Journal of physical chemistry. 2015 June 18, v. 119, no. 24

    2015  

    Abstract: We use flash-photolysis time-resolved microwave conductivity experiments (FP-TRMC) and femtosecond–nanosecond pump–probe transient absorption spectroscopy to investigate photoinduced carrier generation and recombination dynamics of a trilayer cascade ...

    Abstract We use flash-photolysis time-resolved microwave conductivity experiments (FP-TRMC) and femtosecond–nanosecond pump–probe transient absorption spectroscopy to investigate photoinduced carrier generation and recombination dynamics of a trilayer cascade heterojunction composed of poly(3-hexylthiophene) (P3HT), titanyl phthalocyanine (TiOPc), and fullerene (C₆₀). Carrier generation following selective photoexcitation of TiOPc is independently observed at both the P3HT/TiOPc and TiOPc/C₆₀ interfaces. The transient absorption results indicate that following initial charge generation processes to produce P3HT•⁺/TiOPc•– and TiOPc•⁺/C₆₀•– at each interface from (P3HT/TiOPc*/C₆₀), the final charge-separated product of (P3HT•⁺/TiOPc/C₆₀•–) is responsible for the long-lived photoconductance signals in FP-TRMC. At the P3HT/TiOPc interface in both P3HT/TiOPc and P3HT/TiOPc/C₆₀ samples, the electron transfer appears to occur only with the crystalline (weakly coupled H-aggregate) phase of the P3HT.
    Keywords absorption ; electron transfer ; fullerene ; spectroscopy
    Language English
    Dates of publication 2015-0618
    Size p. 7729-7739.
    Publishing place American Chemical Society
    Document type Article
    ISSN 1520-5207
    DOI 10.1021%2Facs.jpcb.5b00110
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  10. Article ; Online: Short and long-range electron transfer compete to determine free-charge yield in organic semiconductors.

    Carr, Joshua M / Allen, Taylor G / Larson, Bryon W / Davydenko, Iryna G / Dasari, Raghunath R / Barlow, Stephen / Marder, Seth R / Reid, Obadiah G / Rumbles, Garry

    Materials horizons

    2022  Volume 9, Issue 1, Page(s) 312–324

    Abstract: Understanding how Frenkel excitons efficiently split to form free-charges in low-dielectric constant organic semiconductors has proven challenging, with many different models proposed in recent years to explain this phenomenon. Here, we present evidence ... ...

    Abstract Understanding how Frenkel excitons efficiently split to form free-charges in low-dielectric constant organic semiconductors has proven challenging, with many different models proposed in recent years to explain this phenomenon. Here, we present evidence that a simple model invoking a modest amount of charge delocalization, a sum over the available microstates, and the Marcus rate constant for electron transfer can explain many seemingly contradictory phenomena reported in the literature. We use an electron-accepting fullerene host matrix dilutely sensitized with a series of electron donor molecules to test this hypothesis. The donor series enables us to tune the driving force for photoinduced electron transfer over a range of 0.7 eV, mapping out normal, optimal, and inverted regimes for free-charge generation efficiency, as measured by time-resolved microwave conductivity. However, the photoluminescence of the donor is rapidly quenched as the driving force increases, with no evidence for inverted behavior, nor the linear relationship between photoluminescence quenching and charge-generation efficiency one would expect in the absence of additional competing loss pathways. This behavior is self-consistently explained by competitive formation of bound charge-transfer states and long-range or delocalized free-charge states, where both rate constants are described by the Marcus rate equation. Moreover, the model predicts a suppression of the inverted regime for high-concentration blends and efficient ultrafast free-charge generation, providing a mechanistic explanation for why Marcus-inverted-behavior is rarely observed in device studies.
    Language English
    Publishing date 2022-01-04
    Publishing country England
    Document type Journal Article
    ZDB-ID 2744250-0
    ISSN 2051-6355 ; 2051-6347
    ISSN (online) 2051-6355
    ISSN 2051-6347
    DOI 10.1039/d1mh01331a
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