Optical studies of triplet excitations in poly(<i>p</i>-phenylene vinylene)

Österbacka, Ronald; Wohlgenannt, M.; Chinn, Douglas; Vardeny, Z. Valy

doi:10.1103/physrevb.60.r11253

Cited by 70 publications

(58 citation statements)

References 27 publications

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“…15. From this measurement we note that the singlet-triplet energy difference ⌬ ST ϭE S ϪE T is approximately 1 eV for the lowest exciton (1B u ), and that similar values for ⌬ ST were also measured in PPV, 36 as well as calculated by recent ab initio band structure calculations. 37 …”

Section: Let Us Call the Distribution Resulting From This Fit Dј(e) supporting

confidence: 85%

“…Also, since ⌬ ST is determined by the exchange interaction, then the large ⌬ ST value (Ϸ1 eV) for the 1B u exciton obtained from our measurements is in agreement with the strong e-e interaction in mLPPP that we deduced from E b . We also note that similar values for ⌬ ST were also measured in PPV, 36 as well as calculated by recent ab initio band structure calculations. 37 The HOMO and lowest unoccupied molecular orbital ͑LUMO͒ levels in the charged manifold ͓Fig.…”

Section: F Excited States Energy Levelssupporting

confidence: 88%

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Photogeneration and recombination processes of neutral and charged excitations in films of a ladder-type poly(para-phenylene)

et al. 1999

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We introduce a version of the cw photomodulation technique, measured far from the steady state, for obtaining the quantum efficiency, , of long-lived photoexcitations in -conjugated polymers. We apply this technique to films of a ladder-type poly͑para-phenylene͒ ͓mLPPP͔ for studying the photogeneration action spectra, (E), and recombination kinetics of photogenerated neutral and charged excitations such as singlet and triplet excitons and charged polarons. Whereas the (E) spectrum for singlet excitons shows a step function increase at a photon energy, E, close to the optical gap (Ӎ2.6 eV), both triplet and polaron (E) spectra show, in addition, a monotonous rise at higher E. The rise for triplets is explained by singlet exciton fission into triplet pairs, and from a model fit we get the triplet exciton energy (Ӎ1.6 eV). For polarons this rise is modeled by an electron intersegment tunneling process. The electroabsorption spectrum is also measured and analyzed in terms of Stark shift of the lowest lying exciton, 1B u , and enhanced oscillator strength of the important mA g exciton. A consistent picture for the lowest excited state energy levels and optical transitions in the neutral ͑singlet and triplet͒ and charged manifolds is presented. From both the exciton binding energy of Ӎ0.6 eV and the singlet-triplet energy splitting of Ӎ1 eV, we conclude that the e-e interaction in mLPPP is relatively strong. Our results are in good agreement with recent ab initio band structure calculations for several -conjugated polymers. ͓S0163-1829͑99͒13531-8͔

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Section: Let Us Call the Distribution Resulting From This Fit Dј(e) supporting

confidence: 85%

Section: F Excited States Energy Levelssupporting

confidence: 88%

Photogeneration and recombination processes of neutral and charged excitations in films of a ladder-type poly(para-phenylene)

et al. 1999

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“…In the pristine polymer, triplet exciton densities can be very high because of the long triplet lifetime, making the triplet-polaron mechanism a likely candidate. The positive sign of the LFE and the width of the HFE (B80 mT), a typical value for the ZFS 31 , is consistent with this interpretation. Very remarkably, we observe that the magnitude of both the LFE and HFE are quenched by adding just a few wt.% PCBM, consistent with PCBM acting as an efficient quencher of excitons.…”

Section: Discussionsupporting

confidence: 78%

“…As such, this provides an alternative route towards unravelling underlying mechanisms. To do so, we performed finite element drift-diffusion simulations 19,31,38,41 for realistic parameters (please refer to the Supplementary Note 3 for more details). Here we will briefly discuss the MC(V) in all three regimes, starting with regime (2).…”

Section: Discussionmentioning

confidence: 99%

Tuning organic magnetoresistance in polymer-fullerene blends by controlling spin reaction pathways

et al. 2013

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Harnessing the spin degree of freedom in semiconductors is generally a challenging, yet rewarding task. In recent years, the large effect of a small magnetic field on the current in organic semiconductors has puzzled the young field of organic spintronics. Although the microscopic interaction mechanisms between spin-carrying particles in organic materials are well understood nowadays, there is no consensus as to which pairs of spin-carrying particles are actually influencing the current in such a drastic manner. Here we demonstrate that the spin-based particle reactions can be tuned in a blend of organic materials, and microscopic mechanisms are identified using magnetoresistance lineshapes and voltage dependencies as fingerprints. We find that different mechanisms can dominate, depending on the exact materials choice, morphology and operating conditions. Our improved understanding will contribute to the future control of magnetic field effects in organic semiconductors.

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“…7 It contains two PA bands DP 1 at 0.1 eV and DP 2 at 1.85 eV, respectively that are due to 2D delocalized polarons in the lamellae, 3,6 -7 as well as PA bands P 1 at 0.35 eV and P 2 at 1.25 eV, respectively, that are due to localized polarons in the disordered portions of the film. 7 In addition, the PA spectrum also contains a PA band IEX at 1.1 eV that was tentatively identified 27 as due to trapped interchain singlet excitons in the lamellae. The -PADMR spectrum measured in RR-P3HT at resonant field that corresponds to gϷ2 due to spin-1 2 carriers is shown in Fig.…”

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confidence: 99%