Zur quantenchemischen Berechnung von indirekten H—H- and 13C—H-Spin-Spin-Kopplungskonstanten von Vinylverbindungen

Steiger, Th.; Gey, E.; Radeglia, R.

doi:10.1515/zpch-1974-01128

Cited by 3 publications

(5 citation statements)

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“…This suggests that their concentration is at the sub-percent level. In the supplemental material we show that the thermally stimulated current (TSC) technique [18] allows the determination of the activation energy of these traps (% 0:5 eV), and also provides a lower limit on the trap concentration of 10 À7 traps per Alq 3 molecule. However, we believe that the actual number of traps is much higher than this lower limit.…”

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confidence: 99%

Tuning the Performance of Organic Spintronic Devices Using X-Ray Generated Traps

et al. 2012

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X rays produced during electron-beam deposition of metallic electrodes drastically change the performance of organic spintronic devices. The x rays generate traps with an activation energy of ≈0.5 eV in a commonly used organic. These traps lead to a dramatic decrease in spin-diffusion length in organic spin valves. In organic magnetoresistive (OMAR) devices, however, the traps strongly enhance magnetoresistance. OMAR is an intrinsic magnetotransport phenomenon and does not rely on spin injection. We discuss our observations in the framework of currently existing theories.

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confidence: 99%

Tuning the Performance of Organic Spintronic Devices Using X-Ray Generated Traps

et al. 2012

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“…However, a more recent investigation by Arkhipov et al [32] on TSC modeling assumed a Gaussian trap distribution with similar shapes as those determined in the present study. Even more recently, Steiger et al [18] proved that for principal reasons a distinction between an exponential and a Gaussian DOS shape is not possible from I-V-characteristics in the investigated temperature regime. Therefore the question whether the observed trap distributions are just occupied tail states of the generally assumed Gaussian distribution of the HOMO and LUMO levels in disordered systems or traps from different origin has to be answered by taking a closer look at the TSC spectra in Fig.…”

Section: Pristine Traps and Their Electronic Structurementioning

confidence: 99%

“…To be able to judge any changes induced upon doping, pristine organic semiconductors have to be investigated. Therefore 200 nm thick single layer structures of the most prominent organic transport materials Alq 3 , α-NPD and 1-NaphDATA were vacuum-deposited between ITO and Al contacts (for details see [18]). If not stated otherwise, traps were optically filled at 80 K for 5 min followed by a thermalization time of another 5 min at 80 K without optical illumination before starting the TSC temperature scan.…”

Section: Pristine Traps and Their Electronic Structurementioning

confidence: 99%

“…The integral of the TSC spectra allows one also to calculate a lower limit for the trap density since in TSC measurements not all released charge contributes to the TSC spectra and not all traps are necessarily filled. For more details see reference [18].…”

Section: Pristine Traps and Their Electronic Structurementioning

confidence: 99%

“…From the electronic structure of Rubrene [41] with its LUMO at 3.15 eV and its HOMO at 5.36 eV and the one of Alq 3 [44] with the LUMO at 3.1 eV and the HOMO at 5.7 eV one would expect from the above said a hole trap of a depth of about 0.35 eV. On the other hand, the observed trap states in pure Alq 3 are related to electrons [18]. The question that has to be answered is whether such an incorporated hole trap has an influence on the occupation of the electron traps.…”

Section: Effect Of Doping On Electronic Trapsmentioning

confidence: 99%

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Electronic traps in organic transport layers

Schmechel

Seggern²

2004

phys. stat. sol. (a)

140

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The knowledge about properties of electronic traps in organic semiconductors is one of the major keys for the understanding and optimization of charge transport in organic devices. In the present article the density of occupied states of the most prominent pristine small molecule systems and selected polymers are reported determined, by fractional thermally stimulated current and luminescence techniques. In order to distinguish between impurity and structurally based traps, model systems of doped as well as differently deposited layers were studied. In addition, the influence of detected traps on steady state I-V and dynamic time-of-flight characteristics are reported. DOS Energy LUMO FWHM: 200meV HOMO Energy LUMO FWHM: 200meV LUMO FWHM: 200meV HOMO HOMOThe charge transport in such amorphous layers is mainly determined by hopping processes between strongly localized molecular states. Therefore, it is not obvious how to distinguish between a trap state and a regular transport state. A way out is given by the transport energy concept first introduced by Monro [1] for amorphous inorganic semiconductors and later extended to amorphous organic semiconductors by several authors [2 -6]. This concept is based on a statistical rule, namely, that a carrier in a deep tail state will most probably escape to a state of energy E t independent on its initial energy in the tail (Fig. 2). This makes the energy level E t to a protruding quantity. E t is called transport energy or escape energy since it describes the level from which a trapped carrier is most probably released to move to a neighbouring site. The transport energy has only a statistical meaning, but its role is similar to that of the band edge or mobility edge in inorganic semiconductors. Consequently, each state below the transport energy is a trap state while states above the transport energy are regular transport states, despite all states are localized. However, the transport energy is a function of temperature. A state acting as trap state at room temperature may become a transport state at lower temperatures. Besides the trap states formed by the tail of the regular HOMO/LUMO level distribution there may exist additional trap states at a discrete energy level or with any arbitrary energy distribution in the gap below the transport energy (see Fig. 3). Structural Defects:Even if there are only molecules of the same species, the HOMO/LUMO levels may vary from molecule to molecule. The exact energy position of the HOMO/LUMO level is not only determined by the chemical structure of the molecule itself but also by the electronic polarisation of its surrounding. In case of polymers the effective conjugation length also affects the position of the HOMO/LUMO level. Structural imperfections will lead to a fluctuating surrounding and in case of polymers to a fluctuating conjugation length. In consequence a distribution of HOMO/LUMO levels has to be expected as presented in Fig. 1. The few states in the tail of this distribution below the transport energy will form the tr...

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Zur Berechnung des π-Beitrages zu den H,H-Kopplungskonstanten von Vinylverbindungen

Steiger¹,

Gey²,

Radeglia³

1975

Molecular Physics

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Zur quantenchemischen Berechnung von indirekten H—H- and 13C—H-Spin-Spin-Kopplungskonstanten von Vinylverbindungen

Cited by 3 publications

References 0 publications

Tuning the Performance of Organic Spintronic Devices Using X-Ray Generated Traps

Tuning the Performance of Organic Spintronic Devices Using X-Ray Generated Traps

Electronic traps in organic transport layers

Zur Berechnung des π-Beitrages zu den H,H-Kopplungskonstanten von Vinylverbindungen

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