Slow charge transfer from pentacene triplet states at the Marcus optimum

Natalie A. Pace; Nadezhda V. Korovina; Tyler T. Clikeman; Sarah Holliday; Devin B. Granger; Gerard M. Carroll; Sanjini U. Nanayakkara; John E. Anthony; Iain McCulloch; Steven H. Strauss; Olga V. Boltalina; Justin C. Johnson; Garry Rumbles; Obadiah G. Reid

doi:10.1038/s41557-019-0367-x

Slow charge transfer from pentacene triplet states at the Marcus optimum

Natalie A. Pace, Nadezhda V. Korovina, Tyler T. Clikeman, Sarah Holliday, Devin B. Granger, Gerard M. Carroll, Sanjini U. Nanayakkara, John E. Anthony, Iain McCulloch, Steven H. Strauss, Olga V. Boltalina, Justin C. Johnson, Garry Rumbles, Obadiah G. Reid

Research output: Contribution to journal › Article › peer-review

36 Scopus citations

Abstract

Singlet fission promises to surpass the Shockley–Queisser limit for single-junction solar cell efficiency through the production of two electron–hole pairs per incident photon. However, this promise has not been fulfilled because singlet fission produces two low-energy triplet excitons that have been unexpectedly difficult to dissociate into free charges. To understand this phenomenon, we study charge separation from triplet excitons in polycrystalline pentacene using an electrochemical series of 12 different guest electron-acceptor molecules with varied reduction potentials. We observe separate optima in the charge yield as a function of driving force for singlet and triplet excitons, including inverted regimes for the dissociation of both states. Molecular acceptors can thus provide a strategic advantage to singlet fission solar cells by suppressing singlet dissociation at optimal driving forces for triplet dissociation. However, even at the optimal driving force, the rate constant for charge transfer from the triplet state is surprisingly small, ~107 s−1, presenting a previously unidentified obstacle to the design of efficient singlet fission solar cells.

Original language	English (US)
Pages (from-to)	63-70
Number of pages	8
Journal	Nature Chemistry
Volume	12
Issue number	1
DOIs	https://doi.org/10.1038/s41557-019-0367-x
State	Published - Nov 25 2019

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: This work was produced in part by the National Renewable Energy Laboratory, operated by Alliance for Sustainable Energy, for the US Department of Energy under Contract No. DE-AC36–08GO28308. Funding provided by the Solar Photochemistry Program of the US Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Biosciences and Geosciences. The views expressed in the article do not necessarily represent the views of the US Department of Energy or the US Government. T.T.C., S.H.S. and O.V.B. thank the National Science Foundation (grants CHE-1012468 and CHE-1362302) for support of the synthesis of PDI acceptors. S.H. and I.M. thank BASF, EPSRC (EP/ G037515/1), EPSRC (EP/L016702/1), EC FP7 Project X10D (287818) and Nanomatcell (308997) for support of the synthesis of rhodanine acceptors. D.B.G. and J.E.A. thank the National Science Foundation (DMREF-1627428) for support of the synthesis of tetracene acceptors. We thank P. Parilla for advice regarding X-ray diffraction crystallite size measurements. We thank E. Pace for creating the table of contents graphic.

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Pace, N. A., Korovina, N. V., Clikeman, T. T., Holliday, S., Granger, D. B., Carroll, G. M., Nanayakkara, S. U., Anthony, J. E., McCulloch, I., Strauss, S. H., Boltalina, O. V., Johnson, J. C., Rumbles, G., & Reid, O. G. (2019). Slow charge transfer from pentacene triplet states at the Marcus optimum. Nature Chemistry, 12(1), 63-70. https://doi.org/10.1038/s41557-019-0367-x

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title = "Slow charge transfer from pentacene triplet states at the Marcus optimum",

abstract = "Singlet fission promises to surpass the Shockley–Queisser limit for single-junction solar cell efficiency through the production of two electron–hole pairs per incident photon. However, this promise has not been fulfilled because singlet fission produces two low-energy triplet excitons that have been unexpectedly difficult to dissociate into free charges. To understand this phenomenon, we study charge separation from triplet excitons in polycrystalline pentacene using an electrochemical series of 12 different guest electron-acceptor molecules with varied reduction potentials. We observe separate optima in the charge yield as a function of driving force for singlet and triplet excitons, including inverted regimes for the dissociation of both states. Molecular acceptors can thus provide a strategic advantage to singlet fission solar cells by suppressing singlet dissociation at optimal driving forces for triplet dissociation. However, even at the optimal driving force, the rate constant for charge transfer from the triplet state is surprisingly small, ~107 s−1, presenting a previously unidentified obstacle to the design of efficient singlet fission solar cells.",

author = "Pace, {Natalie A.} and Korovina, {Nadezhda V.} and Clikeman, {Tyler T.} and Sarah Holliday and Granger, {Devin B.} and Carroll, {Gerard M.} and Nanayakkara, {Sanjini U.} and Anthony, {John E.} and Iain McCulloch and Strauss, {Steven H.} and Boltalina, {Olga V.} and Johnson, {Justin C.} and Garry Rumbles and Reid, {Obadiah G.}",

note = "KAUST Repository Item: Exported on 2020-10-01 Acknowledgements: This work was produced in part by the National Renewable Energy Laboratory, operated by Alliance for Sustainable Energy, for the US Department of Energy under Contract No. DE-AC36–08GO28308. Funding provided by the Solar Photochemistry Program of the US Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Biosciences and Geosciences. The views expressed in the article do not necessarily represent the views of the US Department of Energy or the US Government. T.T.C., S.H.S. and O.V.B. thank the National Science Foundation (grants CHE-1012468 and CHE-1362302) for support of the synthesis of PDI acceptors. S.H. and I.M. thank BASF, EPSRC (EP/ G037515/1), EPSRC (EP/L016702/1), EC FP7 Project X10D (287818) and Nanomatcell (308997) for support of the synthesis of rhodanine acceptors. D.B.G. and J.E.A. thank the National Science Foundation (DMREF-1627428) for support of the synthesis of tetracene acceptors. We thank P. Parilla for advice regarding X-ray diffraction crystallite size measurements. We thank E. Pace for creating the table of contents graphic.",

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doi = "10.1038/s41557-019-0367-x",

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AU - Pace, Natalie A.

AU - Korovina, Nadezhda V.

AU - Clikeman, Tyler T.

AU - Holliday, Sarah

AU - Granger, Devin B.

AU - Carroll, Gerard M.

AU - Nanayakkara, Sanjini U.

AU - Anthony, John E.

AU - McCulloch, Iain

AU - Strauss, Steven H.

AU - Boltalina, Olga V.

AU - Johnson, Justin C.

AU - Rumbles, Garry

AU - Reid, Obadiah G.

N1 - KAUST Repository Item: Exported on 2020-10-01 Acknowledgements: This work was produced in part by the National Renewable Energy Laboratory, operated by Alliance for Sustainable Energy, for the US Department of Energy under Contract No. DE-AC36–08GO28308. Funding provided by the Solar Photochemistry Program of the US Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Biosciences and Geosciences. The views expressed in the article do not necessarily represent the views of the US Department of Energy or the US Government. T.T.C., S.H.S. and O.V.B. thank the National Science Foundation (grants CHE-1012468 and CHE-1362302) for support of the synthesis of PDI acceptors. S.H. and I.M. thank BASF, EPSRC (EP/ G037515/1), EPSRC (EP/L016702/1), EC FP7 Project X10D (287818) and Nanomatcell (308997) for support of the synthesis of rhodanine acceptors. D.B.G. and J.E.A. thank the National Science Foundation (DMREF-1627428) for support of the synthesis of tetracene acceptors. We thank P. Parilla for advice regarding X-ray diffraction crystallite size measurements. We thank E. Pace for creating the table of contents graphic.

PY - 2019/11/25

Y1 - 2019/11/25

N2 - Singlet fission promises to surpass the Shockley–Queisser limit for single-junction solar cell efficiency through the production of two electron–hole pairs per incident photon. However, this promise has not been fulfilled because singlet fission produces two low-energy triplet excitons that have been unexpectedly difficult to dissociate into free charges. To understand this phenomenon, we study charge separation from triplet excitons in polycrystalline pentacene using an electrochemical series of 12 different guest electron-acceptor molecules with varied reduction potentials. We observe separate optima in the charge yield as a function of driving force for singlet and triplet excitons, including inverted regimes for the dissociation of both states. Molecular acceptors can thus provide a strategic advantage to singlet fission solar cells by suppressing singlet dissociation at optimal driving forces for triplet dissociation. However, even at the optimal driving force, the rate constant for charge transfer from the triplet state is surprisingly small, ~107 s−1, presenting a previously unidentified obstacle to the design of efficient singlet fission solar cells.

AB - Singlet fission promises to surpass the Shockley–Queisser limit for single-junction solar cell efficiency through the production of two electron–hole pairs per incident photon. However, this promise has not been fulfilled because singlet fission produces two low-energy triplet excitons that have been unexpectedly difficult to dissociate into free charges. To understand this phenomenon, we study charge separation from triplet excitons in polycrystalline pentacene using an electrochemical series of 12 different guest electron-acceptor molecules with varied reduction potentials. We observe separate optima in the charge yield as a function of driving force for singlet and triplet excitons, including inverted regimes for the dissociation of both states. Molecular acceptors can thus provide a strategic advantage to singlet fission solar cells by suppressing singlet dissociation at optimal driving forces for triplet dissociation. However, even at the optimal driving force, the rate constant for charge transfer from the triplet state is surprisingly small, ~107 s−1, presenting a previously unidentified obstacle to the design of efficient singlet fission solar cells.

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U2 - 10.1038/s41557-019-0367-x

DO - 10.1038/s41557-019-0367-x

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VL - 12

SP - 63

EP - 70

JO - Nature Chemistry

JF - Nature Chemistry

IS - 1

ER -

Slow charge transfer from pentacene triplet states at the Marcus optimum

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