Picosecond time resolved photoluminescence in MEHPPV - solution film, gel and blend

Smilowitz, Laura; Hays, A. K.; Heeger, Alan J.; Wang, G.; Bowers, John E.

doi:10.1016/0379-6779(93)90941-o

Cited by 11 publications

(7 citation statements)

References 12 publications

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“…The fluorescence decay time was 310 ( 30 ps for both solutions; close to previous lifetime estimates of 200-300 ps for similar PPV derivatives. 21,22 The fluorescence spectrum of the dMOM-PPV gel is seen to be quite different at first sight from that of the solutions. However, as for the absorption spectrum, it can be resolved into two similarly shaped components, one of which is identical with that found for the solution and the other red-shifted by ca.…”

Section: Resultsmentioning

confidence: 97%

Polaron Pair Formation, Migration, and Decay on Photoexcited Poly(phenylenevinylene) Chains

1996

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Poly(2-(3,7-dimethyloctoxy)-5-methoxy-1,4-phenylenevinylene), (dMOM-PPV), undergoes a thermochromic transition on heating in benzene at approximately 35°C from a red gel to a yellow solution. The latter is metastable on cooling to room temperature and eventually reverts to the gel form after several hours. The absorption and emission spectrum of the gel can be resolved into two components, one which is identical with that for the solution and which is therefore associated with single-strand segments, and a second of similar spectral shape but lower energy which is ascribed to aggregated segments. Photoexcitation of dMOM-PPV in both the gel and solution results in a transient change in the microwave conductivity as monitored using the time-resolved microwave conductivity (TRMC) technique. The change in microwave conductivity for the gel is approximately an order of magnitude larger than for the solution. No TRMC transient is found on flash photolysis of a benzene solution of a dMOM-PPV derivative with 13% nonconjugated units in the polymer backbone. The effects are attributed to formation of mobile charge carriers (polaron pairs) on a single polymer chain in the case of the solution, whereas in the gel interchain charge transfer results in the predominant formation of charge carriers located on separated chains. The product of the quantum efficiency for polaron pair formation, φ p , and the sum of the mobilities, Σµ, is φ p Σµ ) (2.0 ( 0.3) × 10 -8 m 2 /Vs and (2.0 ( 0.5) × 10 -9 m 2 /Vs for the gel and solution respectively. The decay in microwave conductivity is nonexponential and extends to hundreds of nanoseconds.

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Section: Resultsmentioning

confidence: 97%

Polaron Pair Formation, Migration, and Decay on Photoexcited Poly(phenylenevinylene) Chains

1996

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“…Absorption of photons near the absorption peak wavelength (-500 nm) of the vibronically broadened spectrum randomly excites the different localized chromophores. Under the relatively low excitation conditions of these experiments, only one singlet exciton is present in the molecule during the excited state lifetime (-300 ps) (22,23). Evidence suggests that intramolecular electronic energy transfer (8,15,24) converts the mobile excitons to Wavelength (nm) Fig.…”

Section: Unmasking Electronic Energy Transfer Of Conjugated Polymers mentioning

confidence: 99%

Unmasking Electronic Energy Transfer of Conjugated Polymers by Suppression of O ₂ Quenching

Barbara

2000

Science

375

519

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The photochemistry of poly[2-methoxy, 5-(2'-ethyl-hexyloxy)-p-phenylene-vinylene] (MEH-PPV) has been found to be highly dependent on the presence of O(2), which increases singlet exciton quenching dramatically. Spectroscopy on isolated single molecules of MEH-PPV in polycarbonate films that exclude O(2) reveals two distinct polymer conformations with fluorescence maxima near 555 and 580 nanometers wavelength, respectively. Time-resolved single-molecule data demonstrate that the 580-nanometer conformation exhibits a "landscape" for intramolecular electronic energy relaxation with a "funnel" that contains a 580-nanometer singlet exciton trap at the bottom. The exciton traps can be converted to exciton quenchers by reaction with O(2). Conformationally induced, directed-energy transfer is arguably a critical dynamical process that is responsible for many of the distinctive photophysical properties of conjugated polymers.

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“…The best-fit curves are plotted along with the experimental data in the upper two panels of Figure 10. In the fitting procedure τ fl was fixed at the previously experimentally determined values, i.e., for F8BT τ fl ∼ 3 × 10 -9 s and for MEH-PPV τ fl ∼ 200 × 10 -12 s. 69 The fitting parameters for representative MEH-PPV and F8BT molecules are shown in Table 1. The errors associated with the fitting process are indicated by significant numbers in Table 1.…”

Section: Comparison To Experimentsmentioning

confidence: 99%

Singlet−Triplet and Triplet−Triplet Interactions in Conjugated Polymer Single Molecules

et al. 2005

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Single molecule fluorescence correlation spectroscopy has been used to investigate the photodynamics of isolated single multichromophoric polymer chains of the conjugated polymers MEH-PPV and F8BT on the microsecond to millisecond time scale. The experimental results (and associated kinetic modeling) demonstrate that (i) triplet exciton pairs undergo efficient triplet-triplet annihilation on the <<30 micros time scale, (ii) triplet-triplet annihilation is the dominant mechanism for triplet decay at incident excitation powers > or =50 W/cm(2), and (iii) singlet excitons are quenched by triplet excitons with an efficiency on the order of (1)/(2). The high efficiency of this latter process ensures that single molecule fluorescence spectroscopy can be effectively used to indirectly monitor triplet exciton population dynamics in conjugated polymers. Finally, correlation spectroscopy of MEH-PPV molecules in a multilayer device environment reveals that triplet excitons are efficiently quenched by hole polarons.

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Picosecond time resolved photoluminescence in MEHPPV - solution film, gel and blend

Cited by 11 publications

References 12 publications

Polaron Pair Formation, Migration, and Decay on Photoexcited Poly(phenylenevinylene) Chains

Polaron Pair Formation, Migration, and Decay on Photoexcited Poly(phenylenevinylene) Chains

Unmasking Electronic Energy Transfer of Conjugated Polymers by Suppression of O ₂ Quenching

Singlet−Triplet and Triplet−Triplet Interactions in Conjugated Polymer Single Molecules

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Picosecond time resolved photoluminescence in MEHPPV - solution film, gel and blend

Cited by 11 publications

References 12 publications

Polaron Pair Formation, Migration, and Decay on Photoexcited Poly(phenylenevinylene) Chains

Polaron Pair Formation, Migration, and Decay on Photoexcited Poly(phenylenevinylene) Chains

Unmasking Electronic Energy Transfer of Conjugated Polymers by Suppression of O 2 Quenching

Singlet−Triplet and Triplet−Triplet Interactions in Conjugated Polymer Single Molecules

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Unmasking Electronic Energy Transfer of Conjugated Polymers by Suppression of O ₂ Quenching