Triplet-state photoexcitations of oligothiophene films and solutions

Janssen, René; Smilowitz, Laura; Sariciftci, N. S.; Moses, D.

doi:10.1063/1.467757

Cited by 156 publications

(114 citation statements)

References 54 publications

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“…Lifetimes of 1-to 3-dodecyl-substituted R6, R7, R9, and R11 were determined in frozen 2-methyltetrahydrofuran at 80 K by monitoring the photoinduced absorption assigned as T 1 -T 2 absorption. 27 Lifetimes were 380-470 µs for R6, 350-380 µs for R7, 300 µs for R9, and 250 µs for R11. The trend to shorter lifetimes with increasing number of rings is the same as what we find for R2-R7 (Tables 1 and 2).…”

Section: Resultsmentioning

confidence: 99%

“…Also, no phosphorescence was observed for dodecyl-substituted R6, R7, and longer ones. 27 However, it has been reported 29 that R3 (in undefined environmental and temperature conditions) showed a sharp, single band phosphorescence at 826 nm, which was stated to be identical with that in shape and energy of poly(3-hexylthiophene) in a thin film at 18 K. This phosphorescence emission from R3 seems very strange particularly from the point of view that it is at the same wavelength as a multithiophene component polymerssurely the triplet energies could not be the same. Furthermore, there is some published evidence that the lowest triplet of R3 is near 720 nm (0-0) 30 and we have evidence that it may be at still lower in energy at ∼788 nm (0-0) based on photoacoustical experiments.…”

Section: Resultsmentioning

confidence: 99%

“…Some other data exist for some of the individual oligomers. 1,4,[26][27][28]30 For different alkylsubstituted R9 and R11, T 1 -T n maxima occur at 774 and 805 nm, respectively. 27 The longer (dodecyl) alkyl chain substitutions cause a blue shift in the maxima compared to shorter ones (butyl).…”

Section: Resultsmentioning

confidence: 99%

“…"No" phosphorescence has been abserved by us or others [26][27][28] for R2-R4, although the φ T is very high (0.70-1.0). This is believed to be the result of a large radiationless rate constant.…”

Section: Summary/conclusionmentioning

confidence: 99%

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Comprehensive Evaluation of the Absorption, Photophysical, Energy Transfer, Structural, and Theoretical Properties of α-Oligothiophenes with One to Seven Rings

et al. 1996

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A large basis set of R-oligothiophenes with two to seven rings (R2-R7), also including thiophene, R1, have been investigated in five solvents regarding absorption, fluorescence and phosphorescence, quantum yields of fluorescence (φ F ) and triplet formation (φ T ), lifetimes of fluorescence and the triplet state, quantum yields of singlet oxygen production (φ ∆ ), all rate constants k F , k IC , k ISC , and several of the foregoing as a function of temperature. Ten different theoretical calculations across several levels including three levels of ab initio have been carried out regarding which conformer is lowest in energy and the ∆H's among all conformers of R2, R3 and R5, as well as calculations of transitions energies of the R-oligothiophenes. We have shown that the (l) 1 Bu state is the lowest singlet state for all R2-R7 in any solvent, in contradiction to previous predictions for the higher members. Based on absorption and fluorescence data and calculations of atomic charges in S 0 and S 1 , the ground state is twisted while the excited state is planar (quinoidal-like). Significant charge transfer occurs between S 0 and S 1 but not S 0 and T 1 . For all R2-R7, φ IC is small, k 0 F is approximately constant while k ISC decreases significantly from R2 to R7. The decrease is k ISC is believed to arise from a decrease in matrix elements of the type 〈 1 Ψ CT |H′| 3 Ψ 1 〉. The essential lack of phosphorescence is assigned as originating from inter-ring twisting mode coupling between T 1 and S 0 . Triplet energy transfer to 3 O 2 to produce 1 O 2 is highly efficient for R2-R5. Based on all data, the first Rn representative of R-polythiophene is R5.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Summary/conclusionmentioning

confidence: 99%

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Comprehensive Evaluation of the Absorption, Photophysical, Energy Transfer, Structural, and Theoretical Properties of α-Oligothiophenes with One to Seven Rings

et al. 1996

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“…Using a P3HT density of 1.10 g cm −3 ͑Ref. 17͒ and assuming a chromophore size of 10 repeat units, as deduced from the emission spectra of oligothiophenes, 18 the Förster radius was calculated to be 5.2 nm. The P3HT was spin coated onto fused silica substrates from a 10 mg/ml chloroform solution at 1600 rpm, and the silica spacer was deposited by electron-beam evaporation at a rate in the range of 0.05-0.1 nm s −1 on top of the P3HT, providing a surface and a barrier onto which the PFOBT was spin coated from a 2 mg/ml toluene solution at 4000 rpm.…”

Section: Methodsmentioning

confidence: 99%

Distance dependence of excitation energy transfer between spacer-separated conjugated polymer films

2008

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We report a systematic study of the scaling with distance of electronic energy transfer between thin films of conjugated polymers separated by a silica spacer. The energy-transfer kinetics were obtained directly from time-resolved photoluminescence measurements and show a 1 / z 3 distance dependence of the transfer rate between the excited donor and the acceptor film for z Ն 8 nm. This is consistent with Förster theory; but at shorter separations the energy transfer is slower than predicted and can be explained by the breakdown of the point-dipole approximation at z ϳ 5 nm. The results are relevant for organic photovoltaics and light-emitting devices, where energy transfer can provide a means of increasing performance.

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