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Holt ED, Wang J, Winkel RW, Younus M, Schanze KS. Photophysics and solar cell application of a benzodithiophene conjugated polymer containing cyclometalated platinum units. Journal of Photochemistry and Photobiology 2021. [DOI: 10.1016/j.jpap.2021.100060] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
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Affiliation(s)
- Subhadip Goswami
- Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, United States
| | - Seda Cekli
- Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, United States
| | - Erkki Alarousu
- Solar and Photovoltaics Engineering Research Center, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| | - Russell W. Winkel
- Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, United States
| | - Muhammad Younus
- Department of Chemistry, University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas 78249, United States
| | - Omar F. Mohammed
- Solar and Photovoltaics Engineering Research Center, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| | - Kirk S. Schanze
- Department of Chemistry, University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas 78249, United States
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Cekli S, Winkel RW, Schanze KS. Effect of Oligomer Length on Photophysical Properties of Platinum Acetylide Donor–Acceptor–Donor Oligomers. J Phys Chem A 2016; 120:5512-21. [DOI: 10.1021/acs.jpca.6b03977] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Seda Cekli
- Department
of Chemistry and Center for Macromolecular Science and Engineering, University of Florida, Gainesville, Florida 32611-7200, United States
| | - Russell W. Winkel
- Department
of Chemistry and Center for Macromolecular Science and Engineering, University of Florida, Gainesville, Florida 32611-7200, United States
| | - Kirk S. Schanze
- Department
of Chemistry and Center for Macromolecular Science and Engineering, University of Florida, Gainesville, Florida 32611-7200, United States
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Cekli S, Winkel RW, Alarousu E, Mohammed OF, Schanze KS. Triplet excited state properties in variable gap π-conjugated donor-acceptor-donor chromophores. Chem Sci 2016; 7:3621-3631. [PMID: 29997854 PMCID: PMC6008705 DOI: 10.1039/c5sc04578a] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2015] [Accepted: 02/12/2016] [Indexed: 11/21/2022] Open
Abstract
A series of variable band-gap donor-acceptor-donor (DAD) chromophores capped with platinum(ii) acetylide units has been synthesized and fully characterized by electrochemical and photophysical methods, with particular emphasis placed on probing triplet excited state properties. A counter-intuitive trend of increasing fluorescence quantum efficiency and lifetime with decreasing excited state energy (optical gap) is observed across the series of DAD chromophores. Careful study of the excited state dynamics, including triplet yields (as inferred from singlet oxygen sensitization), reveals that the underlying origin of the unusual trend in the fluorescence parameters is that the singlet-triplet intersystem crossing rate and yield decrease with decreasing optical gap. It is concluded that the rate of intersystem crossing decreases as the LUMO is increasingly localized on the acceptor unit in the DAD chromophore, and this result is interpreted as arising because the extent of spin-orbit coupling induced by the platinum heavy metal centers decreases as the LUMO is more localized on the acceptor. In addition to the trend in intersystem crossing, the results show that the triplet decay rates follow the Energy Gap Law correlation over a 1.8 eV range of triplet energy and 1000-fold range of triplet decay rates. Finally, femtosecond transient absorption studies for the DAD chromophores reveals a strong absorption in the near-infrared region which is attributed to the singlet excited state. This spectral band appears to be general for DAD chromophores, and may be a signature of the charge transfer (CT) singlet excited state.
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Affiliation(s)
- Seda Cekli
- Department of Chemistry and Center for Macromolecular Science and Engineering , University of Florida , Gainesville , Florida 32611-7200 , USA .
| | - Russell W Winkel
- Department of Chemistry and Center for Macromolecular Science and Engineering , University of Florida , Gainesville , Florida 32611-7200 , USA .
| | - Erkki Alarousu
- Solar and Photovoltaics Engineering Research Center , Division of Physical Sciences and Engineering , King Abdullah University of Science and Technology , Thuwal 23955-6900 , Kingdom of Saudi Arabia
| | - Omar F Mohammed
- Solar and Photovoltaics Engineering Research Center , Division of Physical Sciences and Engineering , King Abdullah University of Science and Technology , Thuwal 23955-6900 , Kingdom of Saudi Arabia
| | - Kirk S Schanze
- Department of Chemistry and Center for Macromolecular Science and Engineering , University of Florida , Gainesville , Florida 32611-7200 , USA .
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Goswami S, Gish MK, Wang J, Winkel RW, Papanikolas JM, Schanze KS. π-Conjugated Organometallic Isoindigo Oligomer and Polymer Chromophores: Singlet and Triplet Excited State Dynamics and Application in Polymer Solar Cells. ACS Appl Mater Interfaces 2015; 7:26828-26838. [PMID: 26561718 DOI: 10.1021/acsami.5b09041] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
An isoindigo based π-conjugated oligomer and polymer that contain cyclometalated platinum(II) "auxochrome" units were subjected to photophysical characterization, and application of the polymer in bulk heterojunction polymer solar cells with PCBM acceptor was examined. The objective of the study was to explore the effect of the heavy metal centers on the excited state properties, in particular, intersystem crossing to a triplet (exciton) state, and further how this would influence the performance of the organometallic polymer in solar cells. The materials were characterized by electrochemistry, ground state absorption, emission, and picosecond-nanosecond transient absorption spectroscopy. Electrochemical measurements indicate that the cyclometalated units have a significant impact on the HOMO energy level of the chromophores, but little effect on the LUMO, which is consistent with localization of the LUMO on the isoindigo acceptor unit. Picosecond-nanosecond transient absorption spectroscopy reveals a transient with ∼100 ns lifetime that is assigned to a triplet excited state that is produced by intersystem crossing from a singlet state on a time scale of ∼130 ps. This is the first time that a triplet state has been observed for isoindigo π-conjugated chromophores. The performance of the polymer in bulk heterojunction solar cells was explored with PC61BM as an acceptor. The performance of the cells was optimum at a relatively high PCBM loading (1:6, polymer:PCBM), but the overall efficiency was relatively low with power conversion efficiency (PCE) of 0.22%. Atomic force microscopy of blend films reveals that the length scale of the phase separation decreases with increasing PCBM content, suggesting a reason for the increase in PCE with acceptor loading. Energetic considerations show that the triplet state in the polymer is too low in energy to undergo charge separation with PCBM. Further, due to the relatively low LUMO energy of the polymer, charge transfer from the singlet to PCBM is only weakly exothermic, which is believed to be the reason that the photocurrent efficiency is relatively low.
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Affiliation(s)
- Subhadip Goswami
- Department of Chemistry and Center for Macromolecular Science and Engineering, University, of Florida , P. O. Box 117200, Gainesville, Florida 32611-7200, United States
| | - Melissa K Gish
- Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States
| | - Jiliang Wang
- Department of Chemistry and Center for Macromolecular Science and Engineering, University, of Florida , P. O. Box 117200, Gainesville, Florida 32611-7200, United States
| | - Russell W Winkel
- Department of Chemistry and Center for Macromolecular Science and Engineering, University, of Florida , P. O. Box 117200, Gainesville, Florida 32611-7200, United States
| | - John M Papanikolas
- Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States
| | - Kirk S Schanze
- Department of Chemistry and Center for Macromolecular Science and Engineering, University, of Florida , P. O. Box 117200, Gainesville, Florida 32611-7200, United States
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Abstract
A series of Au(I) and Pt(II) acetylide complexes of a π-conjugated donor-acceptor-donor (D-A-D) chromophore were studied to develop quantitative structure-property relationships for their photophysical and nonlinear optical properties. The D-A-D chromophore consists of a "TBT" unit, where T = 3-hexyl-2,5-thienylene and BTD = 2,1,3-benzothiadiazole, capped with ethynylene groups. The D-A-D chromophore is functionalized with Au(I)PR3 (R = -Me and -Ph) and trans-Pt(II)(PR3)2-CCPh (R = -Me and -Bu) "auxochromes". All of the metal complexes were characterized by ground-state absorption, photoluminescence, nanosecond transient absorption, and two-photon absorption (2PA) spectroscopy. The experiments provided quantitative values of the photophysical parameters, including rates for radiative decay and intersystem crossing (ISC), triplet yields, and two-photon absorption cross sections. Pronounced solvatochromism in the fluorescence spectra suggests an enhanced dipole moment in the excited state of the complexes compared to the unmetalated TBT chromophore. The gold complexes feature larger fluorescence quantum yields and longer emission lifetimes compared to platinum. The Pt(II) complexes exhibit enhanced triplet-triplet absorption, reduced triplet-state lifetimes, and larger singlet oxygen quantum yields, consistent with more efficient ISC compared to the Au(I) complexes. When excited by 100 fs pulses, all of the D-A-D chromophores exhibit moderate two-photon absorption in the near-infrared between 700 and 900 nm. The 2PA cross section for the Au(I) complexes is almost the same as the unmetalated D-A-D chromophore (∼100 GM). The Pt(II) complexes exhibit significantly enhanced 2PA compared to the other chromophores, reaching 1000 GM at 750 nm. Taken together, the results indicate that the Pt(II) center is considerably more effective in inducing singlet-triplet ISC and in enhancing the 2PA cross section. This result reveals the greater promise for Pt(II) acetylides in chromophores for temporal and frequency agile nonlinear absorption.
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Affiliation(s)
- Subhadip Goswami
- Department of Chemistry, Center for Macromolecular Science and Engineering, University of Florida , P.O. Box 117200, Gainesville, Florida 32611, United States
| | - Russell W Winkel
- Department of Chemistry, Center for Macromolecular Science and Engineering, University of Florida , P.O. Box 117200, Gainesville, Florida 32611, United States
| | - Kirk S Schanze
- Department of Chemistry, Center for Macromolecular Science and Engineering, University of Florida , P.O. Box 117200, Gainesville, Florida 32611, United States
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Gundogan AS, Meng X, Winkel RW, Schanze KS. Platinum carbon bond formation via Cu(i) catalyzed Stille-type transmetallation: reaction scope and spectroscopic study of platinum-arylene complexes. Dalton Trans 2015; 44:17932-8. [DOI: 10.1039/c5dt00538h] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The preparation of Pt(ii) complexes of the type trans-L2Pt(Ar)Cl, L2Pt(Ar)2, and L2Pt(Ar)(Ar′) (L = PBu3, Ar = arylene) by CuI catalyzed reaction of cis-(PBu3)2PtCl2 with aryl-stannanes is reported.
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Affiliation(s)
| | - Xiangli Meng
- Department of Chemistry
- University of Florida
- Gainesville
- USA
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Goswami S, Winkel RW, Alarousu E, Ghiviriga I, Mohammed OF, Schanze KS. Photophysics of Organometallic Platinum(II) Derivatives of the Diketopyrrolopyrrole Chromophore. J Phys Chem A 2014; 118:11735-43. [DOI: 10.1021/jp509987p] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Subhadip Goswami
- Department
of Chemistry, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, United States
| | - Russell W. Winkel
- Department
of Chemistry, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, United States
| | - Erkki Alarousu
- Solar
and Photovoltaics Engineering Research Center, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| | - Ion Ghiviriga
- Department
of Chemistry, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, United States
| | - Omar F. Mohammed
- Solar
and Photovoltaics Engineering Research Center, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| | - Kirk S. Schanze
- Department
of Chemistry, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, United States
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Li Y, Winkel RW, Weisbach N, Gladysz JA, Schanze KS. Photophysics of Platinum Tetrayne Oligomers: Delocalization of Triplet Exciton. J Phys Chem A 2014; 118:10333-9. [DOI: 10.1021/jp5021388] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Yongjun Li
- Department
of Chemistry, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, United States
| | - Russell W. Winkel
- Department
of Chemistry, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, United States
| | - Nancy Weisbach
- Chemistry Department, Texas A&M University, P.O. Box 30012, College Station, Texas 77842, United States
| | - John A. Gladysz
- Chemistry Department, Texas A&M University, P.O. Box 30012, College Station, Texas 77842, United States
| | - Kirk S. Schanze
- Department
of Chemistry, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, United States
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Winkel RW, Dubinina GG, Abboud KA, Schanze KS. Photophysical properties of trans-platinum acetylide complexes featuring N-heterocyclic carbene ligands. Dalton Trans 2014; 43:17712-20. [DOI: 10.1039/c4dt01520g] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Platinum acetylide complexes featuring NHC-carbene ligands show enhanced photophysical properties relative to complexes with phosphine ligands.
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