Phosphorescence and Triplet State Energies of Oligothiophenes

Wasserberg, Dorothee; Marsal, P.; Meskers, Stefan C. J.; Janssen, Raj René; Beljonne, David

doi:10.1021/jp0457085

Cited by 68 publications

(96 citation statements)

References 41 publications

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“…frozen 2-methyltetrahydrofuran solution [17] and 9,9-di-nhexylfluorene oligomers in tetrahydrofuran solution [16] even though we only have a limited number of data points. We can apply the same procedure to estimate the ECL of the b-phase even though we only have two data-points that derive from measurements on oligomers.…”

Section: Resultsmentioning

confidence: 99%

“…This value is considerably longer than that of a similar polyfluorene in frozen solution (!5 monomer units), [17] an effect also presumed to result from the increased conjugation-length of the b-phase. [38] As anticipated, the ECL of the b-phase is significantly longer than that in solution and in thin-film, consistent with its extended chain conformation.…”

Section: Resultsmentioning

confidence: 99%

“…[16] A second study on uncapped poly(9,9-dihexylfluorene-2,7-diyl) oligomers in frozen 2-methyltetrahydrofuran solution revealed an ECL estimated to be !5 monomer units. [17] Despite the significant interest in the structural properties of the b-phase [1,8,18,19] and its possible lasing [20] and optoelectronic properties, the ECL has not been reported for the b-phase via a study of short-chain oligomers. Indeed, molecular-structure modeling has indicated that the b-phase is stabilized by the formation of a molecular 'sheath' composed of its octyl side-chains, and thus questions arise as to…”

Section: Introductionmentioning

confidence: 99%

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Observation of the β‐Phase in Two Short‐Chain Oligofluorenes

Tsoi

Charas

Cadby

et al. 2008

Adv Funct Materials

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The polymer poly(9,9‐dioctylfluorene) (PF8) can be driven into a morphological form termed the β‐phase that has enhanced planarity and increased structural rigidity. We show that the β‐phase can be generated in two different fluorene oligomers; a fluorene pentamer, and a short (statistical) oligomer composed of chains having a maximum length of 19 monomer units. By comparing the energy of the zero‐zero phonon line in fluorescence from the β‐phase oligomers with that in the PF8 polymer, we show that the electronic conjugation length of the β‐phase is (30 ± 12) monomer‐units, a value consistent with the persistence length of the molecular chain.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Observation of the β‐Phase in Two Short‐Chain Oligofluorenes

Tsoi

Charas

Cadby

et al. 2008

Adv Funct Materials

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“…There are, however, reports on phosphorescence of thiophene and thiophene-based oligomers. [26][27][28][29] The triplet states of the copolymers were also characterized through transient absorption spectra in MCH solution at 293 K and in the solid state (thin films) ( Figure 5). In addition to ground state depletion at shorter wavelengths, the spectra show intense absorption bands with maxima at longer wavelengths.…”

Section: Resultsmentioning

confidence: 99%

Excited State Properties of Oligophenyl and Oligothienyl Swivel Cruciforms

et al. 2008

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A comprehensive study has been undertaken of the electronic spectral and photophysical properties of two oligophenyl (BPH and BPHF) and one oligothienyl (BTF) swivel cruciforms involving measurements of absorption, fluorescence, and phosphorescence spectra, quantum yields of fluorescence (φ F ), phosphorescence (φ Ph ) and triplet formation (φ T ), lifetimes of fluorescence (τ F ) and of the triplet state (τ T ), and quantum yields of singlet oxygen production (φ ∆ ). From these, all radiative k F and radiationless rate constants, k IC and k ISC , have been obtained in solution. The energies of the lowest lying singlet and triplet excited states were also determined at 293 K. Several of the above properties have also been obtained at low temperature and in the solid state (thin films). In general, for the phenyl oligophenyl (BPH) and for the oligothienyl (BTF) compounds, the radiationless decay channels (φ IC + φ ISC ) are the dominant pathway for the excited-state deactivation, whereas with the fluorene based oligophenyl BPHF the radiative route prevails. In contrast to the general rule found for related oligomers (and polymers) where radiative emission from T 1 is absent, with the compounds studied, phosphorescence has been observed for all of the compounds, indicating that this type of functionalization can lead to emissive triplets. Time-resolved fluorescence decays with picosecond resolution revealed multiexponential (bi-and triexponential) decay laws compatible with the existence of more than one species or conformation in the excited state. These results are discussed on the basis of conformational flexibility in the excited state.

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“…Excited states of thiophene polymers and oligomers have been widely researched, partly because of the many applications of these molecules. [22][23][24][25][26][27][28][29][30][31][32][33][34][35] Despite significant advances in our understanding of oligo-and polythiophene triplets, fundamental aspects remain unclear, including their spatial delocalization. Reported sizes of triplet excited states of oligo-and polythiophenes have ranged from one ring 25,[36][37][38][39][40] to four rings or more.…”

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confidence: 99%

Resonance Raman Spectroscopy of the T₁ Triplet Excited State of Oligothiophenes

Wang

Angelella

Doyle

et al. 2015

J. Phys. Chem. Lett.

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The characterization of triplet excited states is essential for research on organic photovoltaics and singlet fission. We report resonance Raman spectra of two triplet oligothiophenes with n-alkyl substituents, a tetramer and hexamer. The spectra of the triplets are more complex than the ground state, and we find that density functional theory calculations are a useful starting point for characterizing the bands. The spectra of triplet tetrathiophene and hexathiophene differ significantly from one another. This observation is consistent with a T1 excitation that is delocalized over at least five rings in long oligomers. Bands in the 500-800 cm(-1) region are greatly diminished for an aggregated sample of hexathiophene, likely caused by fast electronic dephasing. These experiments highlight the potential of resonance Raman spectroscopy to unequivocally detect and characterize triplets in thiophene materials. The vibrational spectra can also serve as rigorous standards for evaluating computational methods for excited-state molecules.

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Phosphorescence and Triplet State Energies of Oligothiophenes

Cited by 68 publications

References 41 publications

Observation of the β‐Phase in Two Short‐Chain Oligofluorenes

Observation of the β‐Phase in Two Short‐Chain Oligofluorenes

Excited State Properties of Oligophenyl and Oligothienyl Swivel Cruciforms

Resonance Raman Spectroscopy of the T₁ Triplet Excited State of Oligothiophenes

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Phosphorescence and Triplet State Energies of Oligothiophenes

Cited by 68 publications

References 41 publications

Observation of the β‐Phase in Two Short‐Chain Oligofluorenes

Observation of the β‐Phase in Two Short‐Chain Oligofluorenes

Excited State Properties of Oligophenyl and Oligothienyl Swivel Cruciforms

Resonance Raman Spectroscopy of the T1 Triplet Excited State of Oligothiophenes

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Resonance Raman Spectroscopy of the T₁ Triplet Excited State of Oligothiophenes