Electroreflectance studies on the excitons in PTS and DCHD single crystals

Sebastian, L.; Weiser, G.

doi:10.1016/0301-0104(81)85138-5

Cited by 138 publications

(25 citation statements)

References 28 publications

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“…This results in bleaching of the allowed absorption and the appearance of induced absorption bands in the EA spectrum. [13][14][15][16][17][18][19] Samples were mounted in a cold-finger liquid nitrogen cryostat equipped with optical and electrical access. A sinusoidal electric field modulated at 5 kHz was applied to the sample using the reference output of a lock-in amplifier driving a high voltage amplifier.…”

Section: Experimental Methodsmentioning

confidence: 99%

Photophysics of a poly(phenylenevinylene) with alternatingmeta-phenylene andpara-phenylene rings

et al. 2000

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We have investigated the photophysics of the luminescent polymer poly͑1,3-phenylenevinylene-alt-2,5-dioctyloxy-1,4-phenylenevinylene͒ by a variety of optical spectroscopies. The incorporation of alternating meta-phenylene and para-phenylene rings restricts conjugation with respect to poly͑para-phenylenevinylene͒ derivatives. As a consequence, excited states are blueshifted and the nonlinear susceptibility is reduced. Absorption by aggregates, which can be obscured by scattering and interference, is clearly revealed by electroabsorption spectroscopy. The reduced symmetry of 1,3-PPV modifies optical selection rules, resulting in strong overlap of the fluorescence spectrum with excited state absorption by charged polarons.

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Section: Experimental Methodsmentioning

confidence: 99%

Photophysics of a poly(phenylenevinylene) with alternatingmeta-phenylene andpara-phenylene rings

et al. 2000

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“…This value of PPV is only slightly larger than that of ⌬E b Ӎ0.5 eV for polydiacetylenes. [27][28][29] Now we have interpreted the THG spectra of OPV-n in terms of molecular states, and the THG spectrum of PPV by means of band states, this raises the question: What is required for the existence of band or continuum states? A periodic structure is surely needed.…”

Section: A Thg Spectra Of Ppv and Its Oligomersmentioning

confidence: 99%

“…For example, in PDA the CB edge is located approximately 0.5 eV above the exciton which can be concluded from photoconductivity and electroreflection experiments. [27][28][29] The exciton picture of the absorption spectra of conjugated polymers is widely accepted, at least for polydiacetylenes. There is strong experimental evidence from fluorescence investigations 20-23 that it can also be applied to PPV.…”

Section: A Thg Spectra Of Ppv and Its Oligomersmentioning

confidence: 99%

“…26 Hence the existence of the exciton state in PPV is far less clear than in the case of polydiacetylenes ͑PDA's͒, where ⌬E b Ӎ0.5 eV was found consistently in various experiments. [27][28][29] According to recent theories of Abe et al 30 and Guo et al, 31 the energy levels of the exciton absorption and the conduction-band threshold should be visible as two separate three-photon resonance maxima in third-harmonicgeneration ͑THG͒ experiments. THG can be used as a spectroscopic technique, if the fundamental laser frequency is varied.…”

Section: Introductionmentioning

confidence: 95%

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Third-harmonic-generation spectroscopy of poly(p-phenylenevinylene): A comparison with oligomers and scaling laws for conjugated polymers

et al. 1996

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The third-order nonlinear optical susceptibility ͑3͒ ͑Ϫ3;,,͒ of thin films of poly͑p-phenylenevinylene͒ ͑PPV͒ and several corresponding oligomers ͑OPV-n͒ has been investigated by third-harmonic generation using variable laser wavelengths from 900 to 1520 nm. The oligomers show a single three-photon resonance of ͑3͒ ͑Ϫ3;,,͒ which is closely related to the linear absorption spectrum. We can identify, however, two maxima in the ͑3͒ spectrum of PPV. They are assigned to three-photon resonances with the maximum of the exciton absorption and with the threshold of the continuum of states, which can be located at 3.2Ϯ0.1 eV. This corresponds to an exciton binding energy of 0.7Ϯ0.1 eV. We observe a general scaling behavior for PPV, OPV-n, and other one-dimensional conjugated -electron systems in their neutral form. Their ͑3͒ values, evaluated at comparable resonant or low-resonant conditions, follow an empirical scaling relationship(3) /␣ max ϳ max x , where ␣ max and max denote the absorption coefficient and wavelength of the low-energy absorption maximum. We obtain an exponent xϭ10Ϯ1 which is much larger than expected from an earlier theory. Possible reasons for the difference between theory and experimental results are discussed.

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“…Under a strong applied electric field, a significant Stark shift would manifest in the spectra near the absorption edge, as seen previously in electroabsorption measurements. [42][43][44][45][46][47][48][49][50][51] We do observe some additional structure in the bleached absorption above the band edge in Fig. 4.…”

Section: Resultsmentioning

confidence: 60%

Electron and hole polaron accumulation in low-bandgap ambipolar donor-acceptor polymer transistors imaged by infrared microscopy

et al. 2014

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A resurgence in the use of the donor-acceptor (DA) approach in synthesizing conjugated polymers has resulted in a family of high-mobility ambipolar systems with exceptionally narrow energy bandgaps below 1 eV. The ability to transport both electrons and holes is critical for device applications such as organic light-emitting diodes (OLEDs) and transistors (OLETs). Infrared spectroscopy offers direct access to the low-energy excitations associated with injected charge carriers. Here we use a diffraction-limited IR microscope to probe the spectroscopic signatures of electron and hole injection in the conduction channel of an organic field-effect transistor (OFET) based on an ambipolar DA polymer polydiketopyrrolopyrrole-benzobisthiadiazole (PDPPBBT). We observe distinct polaronic absorptions for both electrons and holes, and spatially map the carrier distribution from the source to drain electrodes for both unipolar and ambipolar biasing regimes. For ambipolar device configurations, we observe the spatial evolution of hole-induced to electron-induced polaron absorptions throughout the transport path. Our work provides a platform for combined transport and infrared studies of organic semiconductors on micron length scales relevant to functional devices.

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Electroreflectance studies on the excitons in PTS and DCHD single crystals

Cited by 138 publications

References 28 publications

Photophysics of a poly(phenylenevinylene) with alternatingmeta-phenylene andpara-phenylene rings

Photophysics of a poly(phenylenevinylene) with alternatingmeta-phenylene andpara-phenylene rings

Third-harmonic-generation spectroscopy of poly(p-phenylenevinylene): A comparison with oligomers and scaling laws for conjugated polymers

Electron and hole polaron accumulation in low-bandgap ambipolar donor-acceptor polymer transistors imaged by infrared microscopy

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