Ultrafast Field-Induced Dissociation of Excitons in Conjugated Polymers

Kersting, R.; Lemmer, Uli; Deussen, M.; Bakker, Huib J.; Mahrt, Rainer F.; Kurz, H.; Arkhipov, V. I.; Bäßler, H.; Göbel, E. O.

doi:10.1103/physrevlett.73.1440

Cited by 323 publications

(216 citation statements)

References 19 publications

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“…[43][44][45][46][47] and others supporting the exciton dissociation picture. [48][49][50] There also exists a dramatic difference in the magnitude of the measured mobility. Since mobility is an important concept in understanding and improving the device performance, an accurate measurement is essential.…”

Section: Zheng Et Almentioning

confidence: 99%

Organic Broadband TeraHertz Sources and Sensors

Zheng¹,

McLaughlin²,

Cunningham³

et al. 2007

Journal of Nanoelectronics and Optoelectronics

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We review recent research using organic materials for generation and detection of broadband terahertz radiation (0.3 THz−30 THz). The main focus is on amorphous electrooptic (EO) polymers, with semiconducting polymers, molecular salt EO crystals, and molecular solutions briefly discussed. The advantages of amorphous EO polymers over other materials for broadband THz generation (via optical rectification) and detection (via EO sampling) include a lack of phonon absorption (good transparency) in the THz regime, high EO coefficient and good phase-matching properties, and, of course, easy fabrication (low cost). Our ∼12-THz, spectral gap-free THz system based on a polymer emitter-sensor pair is an excellent demonstration of the advantages using of EO polymers. We also present a model that can predict the performance of a polymer-based THz system. Both the dielectric properties of an EO polymer and laser pulse related parameters are included in the model, making the simulations close to real conditions. From our modeling work, the roles the dielectric properties play in the THz generation and detection are clearly seen, providing us with a good guide to select and design suitable EO polymers in the future.

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Section: Zheng Et Almentioning

confidence: 99%

Organic Broadband TeraHertz Sources and Sensors

Zheng¹,

McLaughlin²,

Cunningham³

et al. 2007

Journal of Nanoelectronics and Optoelectronics

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“…21 Figure 1͑b͒ shows a (⌬T) MF spectrum obtained for a delay of 20 ps and an applied reverse bias of 16 V. We observe a transient decrease of SE ͓negative (⌬T/T) MF signal͔ and PA 1 ͓positive (⌬T/T) MF signal͔ that can be explained by field-induced dissociation of the singlet exciton population, similar to the effect under steady-state condition. [22][23][24][25] We emphasize that the correlated decrease of SE and PA 1 is a further indication for the assignment of PA 1 to singlet exciton transitions, whereas both PA 2 and PA 3 are increased by the applied field ͓negative (⌬T/T) MF signal͔, indicating a corresponding increase of polaron and triplet population. The normalized field-induced changes of the populations are plotted in Fig.…”

Section: B Electric Field-assisted Pump-probe Spectroscopymentioning

confidence: 99%

Ultrafast photogeneration mechanisms of triplet states inpara-hexaphenyl

et al. 1999

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We present femtosecond pump-probe measurements, both conventional and electric field-assisted, on organic light-emitting devices based on para-hexaphenyl. The dominant triplet exciton generation mechanism is assigned to nongeminate bimolecular recombination of photogenerated, spin-1 2 polarons. This process is active within a few hundred femtoseconds after photoexcitation and involves about 20% of the initially excited states. At higher photoexcitation densities, we observe an additional triplet generation mechanism, which occurs in the 10-ps time domain, due to fusion of singlet excitons and subsequent fission into correlated triplet pairs. The latter decay on the 10 2 -ps time scale by geminate recombination. ͓S0163-1829͑99͒01721-X͔

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“…The result of this is that the data become complicated by the simultaneous observation of many processes and often small differences in the experimental conditions can change the dominance of the various processes, and therefore conclusions obtained can appear inconsistent. [12][13][14][15][16] In many cases, the intensity dependent phenomena observed are present at the lowest excitation densities measured and as a result it can be difficult to reconcile with data from experiments such as time resolved fluorescence measurements which only require very low pump fluence. 11,17 The result is that time resolved measurements on conjugated polymers often fall into two categories, high pump dose and low pump dose with little data available in the crossover.…”

Section: Introductionmentioning

confidence: 99%

Exciton annihilation in a polyfluorene: Low threshold for singlet-singlet annihilation and the absence of singlet-triplet annihilation

et al. 2007

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(2007) 'Exciton annihilation in a polyuorene : low threshold for singlet-singlet annihilation and the absence of singlet-triplet annihilation. ', Physical review B., 76 (8) Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Ultrafast photoinduced absorption measurements have been used to directly investigate singlet-singlet annihilation in polyfluorene. The pump fluence threshold for annihilation to dominate the decay was measured to be ϳ1 J cm −2 corresponding to an excitation density of 1.5ϫ 10 17 cm −3 . The annihilation rate was found to be faster than that expected from a simple dipole-dipole interaction. This is ascribed to the additional influence of diffusion which, because of the dispersive nature of the exciton migration, has strong time dependence as the singlet excitons thermalize in the density of states as well as the expected intrinsic time dependence from a diffusion controlled process. Also, a comparable background level of triplets was created in the film to study the effect of singlet-triplet annihilation, which surprisingly, given the low threshold for singlet-singlet annihilation, was found to be negligible.

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Ultrafast Field-Induced Dissociation of Excitons in Conjugated Polymers

Cited by 323 publications

References 19 publications

Organic Broadband TeraHertz Sources and Sensors

Organic Broadband TeraHertz Sources and Sensors

Ultrafast photogeneration mechanisms of triplet states inpara-hexaphenyl

Exciton annihilation in a polyfluorene: Low threshold for singlet-singlet annihilation and the absence of singlet-triplet annihilation

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