One-Dimensional Wide Energy Bands in a Polydiacetylene Revealed by Electroreflectance

Sebastian, L.; Weiser, G.

doi:10.1103/physrevlett.46.1156

Cited by 216 publications

(97 citation statements)

References 11 publications

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“…It has been shown that R/R < 10 −6 for organic semiconductors 31 and thus changes in reflectance can be neglected in the case of the much stronger electromodulation seen here. Taking into account that the absorption coefficient is equal to the product of the excitation density (n) and the absorption cross section (σ ), we arrive at the final relation:…”

Section: Field-modulated Excited State Absorptionmentioning

confidence: 94%

“…The field causes a Stark shift of energy levels, resulting in an EA spectrum proportional to the square of the electric field and the imaginary part of the third order dc Kerr nonlinear susceptibility, χ (3) (-ω;0,0,ω). 31 To the lowest order and for a material without a permanent dipole moment in its ground state or lowest excited state, the EA spectrum of a material will follow the first derivative of the absorption spectrum with respect to energy. For an unoriented material with a difference in the dipole moment in the ground and excited states, the EA spectrum will follow the second derivative of the absorption spectrum with respect to energy.…”

Section: Introductionmentioning

confidence: 99%

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Electromodulated doping of the hole transport layer in a small molecule organic light-emitting diode

Lane

2011

J. Photon. Energy

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Abstract. Electromodulation spectroscopy has been used to probe the effect of a polymer hole injection layer on electric fields and charge injection in vacuum-deposited organic light-emitting diodes. The electromodulation spectrum consists of electroabsorption of the transport layers and excited state absorption of trapped cations in the hole transport layer. Field-dependent modulation of trapped charge at the interface between the injection and transport layers substantially modifies the electric field distribution within the device. In reverse bias, the electric field strength is suppressed within the hole transport layer and concentrated in the electron transport layer. In forward bias, field-dependent doping of the hole transport layer dominates the electromodulation spectrum. The field-dependent trap density is calculated to be of order 10 13 cm −2 , equivalent to μC/cm 2 charge density. The built-in potential is estimated to be between 2.2 and 2.5 V, consistent with low carrier injection barriers. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

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Section: Field-modulated Excited State Absorptionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Electromodulated doping of the hole transport layer in a small molecule organic light-emitting diode

Lane

2011

J. Photon. Energy

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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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“…The resulting spectra, to a good approximation, are proportional to the imaginary part of the dc Kerr susceptibility, (3) (Ϫ ;0,0, ), since ϳ10 15 Hz. A number of conjugated polymers have been studied by EA spectroscopy, including polyacetylene, 5 polydiacetylenes-͑PDA͒, 6 and polythieneylenevinylene ͑PTV͒. 7 In general these studies have found that the EA spectra reasonably closely follow a combination of first and second energy derivatives of the linear absorption spectrum.…”

Section: Introductionmentioning

confidence: 99%

Linear and nonlinear optical properties of the conjugated polymers PPV and MEH-PPV

et al. 1999

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We have used absorption and electroabsorption spectroscopy to investigate the electronic structure of poly͑para-phenylene vinylene͒ ͑PPV͒ and poly "2-methoxy, 5-(2Ј-͑ethyl͒hexyloxy͒-p-phenylene vinylene… ͑MEH-PPV͒. In particular we examine the often used assumption that the electronic structure of PPV and its dialkoxy substituted derivatives are essentially the same. The absorption spectrum of PPV consists of three peaks, while that of MEH-PPV has four peaks. We discuss the controversial origin of the extra peak as well as evidence for Davydov splitting effects in the absorption spectrum of PPV. The analysis of the nonlinear spectra shows further differences between the two materials. First, the binding energy of the 1B u exciton for PPV is some 0.1 eV higher than for MEH-PPV. Second, the peak value of Im͕ (3) (Ϫ ;0,0, )͖ for PPV is approximately 40 times higher than that of MEH-PPV. We also found that the sum-over-states modeling of the electroabsorption spectra indicates that the transition dipole moment between the mA g and nB u states is of opposite sign in the two polymers. ͓S0163-1829͑99͒02523-0͔

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One-Dimensional Wide Energy Bands in a Polydiacetylene Revealed by Electroreflectance

Cited by 216 publications

References 11 publications

Electromodulated doping of the hole transport layer in a small molecule organic light-emitting diode

Electromodulated doping of the hole transport layer in a small molecule organic light-emitting diode

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

Linear and nonlinear optical properties of the conjugated polymers PPV and MEH-PPV

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