Hole formation and transfer in poly[9,9-di(ethylhexyl)fluorene] and an amine end-capped derivative in solution

Burrows, Hugh D.; Melo, J. Sérgio Seixas de; Förster, Michael; Güntner, R.; Scherf, Ullrich; Monkman, Andrew P.; Navaratnam, S.

doi:10.1016/j.cplett.2003.12.061

Cited by 47 publications

(39 citation statements)

References 34 publications

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“…[4,5] Complexity results from photophysical processes, which in dilute solution include solvent and/or conformational relaxation [3,[6][7][8][9][10] and intrachain energy transfer, [11][12][13] while in concentrated solution or in films they may also involve interchain energy transfer, [2] excimer formation [14] and formation of H or J aggregates. [15][16][17] The correct interpretation of this information is important for detecting, understanding and resolving problems such as imbalance of electron and hole injection currents, [18][19][20][21][22][23] decreased luminescence yields, which result from aggregation quenching that is dependent on the polymer concentration, [15][16][17] and chemical stability of the films.…”

Section: Introductionmentioning

confidence: 99%

Photodynamics of a PV Trimer in High‐Viscosity Solvents and in PMMA Films: A New Insight into Energy Transfer versus Conformational Relaxation in Conjugated Polymers

Paolo¹,

Morgado

Maçanita³

2009

ChemPhysChem

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Non-Stokes-Einstein relaxation: The rate constant of conformational relaxation of a phenylenevinylene trimer (see picture) in different solvents is proportional to eta(-alpha), with alpha values decreasing from close to unity (low viscosity) to zero at sufficiently high solvent viscosity. This behaviour is attributed to the flexible methylbutyl side chains of the trimer, which partially screen the solvent friction. The p-phenylenevinylene (PV) trimer (MBOPV3) was used to probe the effect of conformational relaxation on fluorescence decays of PV-based polymers in the high solvent viscosity regime, from n-hexadecane (3.45 cP at 293 K) to liquid paraffin (123 cP at 293 K), and in dilute poly(methyl methacrylate) (PMMA) solid films. The effect of intermolecular energy transfer and radiative transport on the fluorescence decays was also analysed by increasing the concentration of MBOPV3 in the PMMA films up to a pure MBOPV3 film. The rate constant of conformational relaxation was found to decrease with increasing solvent viscosity up to about 23 cP, but then becomes viscosity independent. The non-Stokes-Einstein behaviour of k(CR) versus eta over the whole viscosity range apparently results from the presence of the flexible methylbutyl side chains of MBOPV3, which partially screens the solvent friction. Conformational relaxation is not observed in very dilute PMMA solid films, where the fluorescence decay becomes single exponential. The decays become multi-exponential again with an increase of MBOPV3 concentration in the PMMA films, but in this case it is due to intermolecular (interchain) energy transfer from less planar to more planar conformations of MBOPV3. In the pure MBOPV3 film, interchain energy transfer (radiative and non-radiative) is the major process responsible for the observed (tetra-exponential) decays.

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Section: Introductionmentioning

confidence: 99%

Photodynamics of a PV Trimer in High‐Viscosity Solvents and in PMMA Films: A New Insight into Energy Transfer versus Conformational Relaxation in Conjugated Polymers

Paolo¹,

Morgado

Maçanita³

2009

ChemPhysChem

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“…13 Pulse radiolysis and doping induced absorption studies also provide strong evidence that this feature is the absorption of the polyfluorene cation. 25 The clear isobestic point at 2.15 eV is a strong evidence that the charged state is formed as a direct result of the decay of the singlet exciton: it is a quenching product of the singlet exciton. The lack of absorption in this region immediately after photoexcitation is a direct proof that the charge carriers are not generated directly by optical absorption in this case.…”

Section: Singlet-singlet Annihilationmentioning

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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“…Aromatic amines play this role efficiently by decreasing the mobility of the positive charge carriers, and also reducing the electric field difference between the anode and cathode. [5,6] In addition, they frequently increase the chemical stability of these systems.…”

Section: Introductionmentioning

confidence: 99%

Picosecond Structural Relaxation of Abietic Acid Based Amine End Capped Para‐Phenylenevinylene Trimers in Solution

Paolo¹,

Gigante

Esteves

et al. 2008

ChemPhysChem

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Hole formation and transfer in poly[9,9-di(ethylhexyl)fluorene] and an amine end-capped derivative in solution

Cited by 47 publications

References 34 publications

Photodynamics of a PV Trimer in High‐Viscosity Solvents and in PMMA Films: A New Insight into Energy Transfer versus Conformational Relaxation in Conjugated Polymers

Photodynamics of a PV Trimer in High‐Viscosity Solvents and in PMMA Films: A New Insight into Energy Transfer versus Conformational Relaxation in Conjugated Polymers

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

Picosecond Structural Relaxation of Abietic Acid Based Amine End Capped Para‐Phenylenevinylene Trimers in Solution

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