Charge-carrier dipole traps caused by orientational defects in carbazole crystals

Kadashchuk, A.; Ostapenko, N. I.; Skryshevski, Yu.; Izvekov, S. V.; Sugakov, V. I.

doi:10.1016/s0022-2313(99)00153-2

Cited by 5 publications

(3 citation statements)

References 25 publications

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“…An alternative approach to the DFT model described here could be an approach based on the vibrational exciton model similar to the approach of Ostapenko. − This approach was not directly applicable; if applied to molecular crystals composed of organic molecules that are exposed to highly anisotropic stresses which generate highly anisotropic strain fields, it would lead to exceedingly large number of adjustable parameters. We also note the work of Ordon, Komorowski, and their collaborators on the mechanical perturbation of molecular systems, − however their work focuses on aspects other than the effect of crystal deformation on the molecular vibrations.…”

Section: Resultsmentioning

confidence: 99%

Probing Structural Perturbation in a Bent Molecular Crystal with Synchrotron Infrared Microspectroscopy and Periodic Density Functional Theory Calculations

et al. 2017

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The range of unit cell orientations generated at the kink of a bent single crystal poses unsurmountable challenges with diffraction analysis and limits the insight into the molecular-scale mechanism of bending. On a plastically bent crystal of hexachlorobenzene, it is demonstrated here that spatially resolved microfocus infrared spectroscopy using synchrotron radiation can be applied in conjunction with periodic density functional theory calculations to predict spectral changes or to extract information on structural changes that occur as a consequence of bending. The approach reproduces well the observed trends, such as the wall effects, and provides estimations of the vibrational shifts, unit cell deformations, and intramolecular parameters. Generally, expansion of the lattice induces red-shift while compression induces larger blue-shift of the characteristic ν(C-C) and ν(C-Cl) modes. Uniform or non-uniform expansion or contraction of the unit cell of 0.1 Å results in shifts of several cm, whereas deformation of the cell of 0.5° at the unique angle causes shifts of <0.5 cm. Since this approach does not include parameters related to the actual stimulus by which the deformation has been induced, it can be generalized and applied to other mechanically, photochemically, or thermally bent crystals.

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Section: Resultsmentioning

confidence: 99%

Probing Structural Perturbation in a Bent Molecular Crystal with Synchrotron Infrared Microspectroscopy and Periodic Density Functional Theory Calculations

et al. 2017

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“…Furthermore, we propose that, owing to the conformational flexibility of these groups (i.e., rotational energy barrier of ∼0.3 kJ/mol), MA + reorientational dynamics on <1 ns time scales lead to shallow carrier trapping via charge-dipole interactions. Similar orientational shallow trap mechanisms have been found in polar organic crystals; however, in the case of MAPbX 3 perovskites, dipole reorientation is much more facile. MA + dynamics are also known to screen carrier Coulombic interactions leading to longer carrier lifetimes, which, based on field-dependent PL decays in Figure , is consistent with large fluctuations in the slow and fast component decay times.…”

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confidence: 99%

Modulating Charge Recombination and Structural Dynamics in Isolated Organometal Halide Perovskite Crystals by External Electric Fields

Qiu

Grey

2015

J. Phys. Chem. Lett.

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Time-resolved photoluminescence (PL) of isolated methylammonium lead tribromide (MAPbBr3) perovskite crystalline platelets is studied under applied electric fields to understand the influence of ion conformational and translational dynamics on charge recombination dynamics. MAPbBr3 PL decays and intensity transients over ∼100 ps to 10 s time scales show large modulation upon application of electric fields up to ∼ ±10(7) V/m that we attribute primarily to reorientation of the methylammonium cation (MA(+)) dipole moments. On longer time scales, a large fraction of electric field-dependent PL intensity transients exhibit oscillatory behavior and undergo spontaneous switching on time scales comparable to ion drift (∼1-10 s). PL modulation behavior decreases significantly with aging, suggesting diminished reorientational susceptibility (conformational flexibility) of MA(+) groups to applied electric fields.

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“…From the viewpoint of the electronic property, the effect of the dipole moment of the dopant may be considered. If the dopant with a carboxyl group has a large dipole moment, we can assume that its dipole electric charge traps the positively charged water generated by the friction − and that the penetration of the charged water into the film is prevented. Figure shows the relation between the dipole moment of the dopant and the HD value.…”

Section: Resultsmentioning

confidence: 99%

Unexpected and Unusual Triboelectrification Behavior of Polymer Films Containing Carboxyl Group

et al. 2013

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The triboelectrification behavior of polymer films when in contact with iron carrier beads was investigated using a homemade special instrument which can control relative humidity under a nitrogen atmosphere. The films showed a large humidity-dependent charging behavior; the charge amount increases with the ambient humidity in the range of a few percent RH to ca. 60% RH. This dependence is explained in terms of the model based on the water charging during the friction and the penetration of the positively charged water into the film. However, it was found that the humidity dependence is significantly depressed by the doping of carboxylic acids into the film or by the introduction of a carboxyl group in the polymer backbone. This depression is again explained by the above charged-water penetration model in which carboxylate ions trap the positively charged water on the film surface.

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Charge-carrier dipole traps caused by orientational defects in carbazole crystals

Cited by 5 publications

References 25 publications

Probing Structural Perturbation in a Bent Molecular Crystal with Synchrotron Infrared Microspectroscopy and Periodic Density Functional Theory Calculations

Probing Structural Perturbation in a Bent Molecular Crystal with Synchrotron Infrared Microspectroscopy and Periodic Density Functional Theory Calculations

Modulating Charge Recombination and Structural Dynamics in Isolated Organometal Halide Perovskite Crystals by External Electric Fields

Unexpected and Unusual Triboelectrification Behavior of Polymer Films Containing Carboxyl Group

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