Charge Transport in Amorphous Organic Semiconductors: Effects of Disorder, Carrier Density, Traps, and Scatters

Li, Haoyuan; Li, Chen; Duan, Lian; Qiu, Yong

doi:10.1002/ijch.201400057

Cited by 39 publications

(29 citation statements)

References 78 publications

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“…For the organic semiconductor sites, the site energy is assumed to have a Gaussian distribution, and the density of electronic states (DOS), g ( E ), writes as

g (E) = \frac{1}{\sqrt{2 π σ^{2}}} \exp (- \frac{E^{2}}{2 σ^{2}})

where σ is the energetic disorder. Typical values of the energetic disorder in organic semiconductors are in the range of 50–150 meV . In this study, we vary σ in the range of 51–103 meV, made to correspond to 2 k B T –4 k B T at room temperature (with T being the temperature and k B the Boltzmann constant).…”

Section: Methodsmentioning

confidence: 99%

Organic Field‐Effect Transistors: A 3D Kinetic Monte Carlo Simulation of the Current Characteristics in Micrometer‐Sized Devices

et al. 2017

Adv Funct Materials

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1605715(1 of 11) devices; as a result, the current characteristics predicted by these models often deviate from those measured in actual OFETs. [2] Therefore, in order to gain a better understanding of the OFET device physics, it is highly desirable to develop more robust models that go beyond approximations that could be inappropriate for organic semiconductors. [2d] As a matter of fact, the electrical currents in the device are intimately related to the microscopic mechanisms of charge transport. In the vast majority of organic semiconductor thin films, the charge transport can be described by hopping of charge carriers (polarons) among localized electronic states. [3] Such a process, however, is in fact ignored in most OFET models. On the other hand, detailed information on microscopic charge transport is required when modeling an OFET device. For example, the distribution of charge carriers is needed to evaluate the drain current, which is directly related to the charge-transport process. Without explicit consideration of the nature of the microscopic charge transport, such information has to be obtained by relying on even more assumptions. A commonly used approximation is the so-called gradual channel approximation (GCA), which can provide simple solutions for the current-voltage relationships in OFETs when further assuming zero channel thickness, no diffusion, and constant mobility. Importantly, most of these assumptions have not been shown to be valid, in particular over the full data range, in the case of OFETs. For instance, the GCA implies that, when the gate voltage (V G ) is much larger than the drain voltage (V D ), the 2D electric potential can be simplified as a linear combination of two 1D profiles along orthogonal directions. [4] Thus, the GCA is valid in principle only in a narrow range in the linear regime of the OFET characteristics (i.e., when V D ≪ V G ); in practice, however, the GCA is used in the interpretation of the experimental data in both the linear and saturation regimes (i.e., even when V D > V G ), which in the latter case is clearly in contradiction with the prerequisite for the GCA. Indeed, in the saturation regime (and also some sections of the linear regime), the strength of the lateral electric field becomes comparable to that of the perpendicular field, so that the device physics near the drain electrode cannot be accounted for by the GCA. Moreover, the charge mobilities of organic semiconductor have The electrical properties of organic field-effect transistors (OFETs) are usually characterized by applying models initially developed for inorganic-based devices, which often implies the use of approximations that might be inappropriate for organic semiconductors. These approximations have brought limitations to the understanding of the device physics associated with organic materials. A strategy to overcome this issue is to establish straightforward connections between the macroscopic current characteristics and microscopic charge transport in OFETs. Here, a 3D kinetic Mon...

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“…For the organic semiconductor sites, the site energy is assumed to have a Gaussian distribution, and the density of electronic states (DOS), g ( E ), writes as

g (E) = \frac{1}{\sqrt{2 π σ^{2}}} \exp (- \frac{E^{2}}{2 σ^{2}})

Section: Methodsmentioning

confidence: 99%

Organic Field‐Effect Transistors: A 3D Kinetic Monte Carlo Simulation of the Current Characteristics in Micrometer‐Sized Devices

et al. 2017

Adv Funct Materials

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“…Hence, the thermal activation energy needed for the re-mobilization of trapped charge carriers is lowered in the presence of strong electrostatic fields. As a consequence, the immobilization of charge carriers is more prominent in case of rather weak fields, and the effective mobility of charge carriers increases with increasing field strength [15].The authors have observed the analogous effects in case of current transport through macroscopic dust layers as well [10,11].…”

Section: Mechanisms Of Charge Transportmentioning

confidence: 79%

“…In addition to the kinetic effects resulting from charge carrier trapping, detrapping and recombination, current transport through dielectrics is controlled by the space charge effect [10][11][12][13][14][15]. Each charge carrier, mobile or trapped, contributes to the space charge according to its polarity.…”

Section: Mechanisms Of Charge Transportmentioning

confidence: 99%

Force and current in a contact gap between single highly resistive particles: experimental observations

2019

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In case of electrical conduction through highly resistive dust layers, the generation of electrostatic adhesion force is strongly coupled to the mechanism of electrical (current) transport in the solid. High field strengths lead to a significant increase of the adhesive force. Here, more insight into the underlying mechanisms is given by experiments on the microscopic scale. An experimental arrangement is described which allows to study a particle pair subject to a strong electric field. Both the current and the force between the particles (150 μm) can be measured as a function of voltage and gap distance. The results show an extremely complex behaviour of the contact for the case of highly resistive particles. For current transport, both gas discharges and thermionic field emission are observed, depending on the width of the contact gap and the field strength. For both the force and the current across the gap, a strongly non-linear behaviour with pronounced time effects is observed.But additional problems are found with highly resistive dusts in electrostatic precipitators (ESPs). With dust resistivities beyond 10 11 Ω-cm, the precipitation process itself is disturbed by so called back corona (Masuda in [2,(3)(4)(5)). The current interpretation is that the current has to pass through the dust layer on the precipitation electrode. With high dust resistivity, a given current density will cause a strong voltage-drop across the dust layer and hence a strong electric field inside the dust layer. When a critical field strength is surpassed, an electric breakthrough occurs.

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“…Benefitting from the suppressed hole trap, holes can be accumulated either on host or on dopant. After recombination with the injected electrons via an electrostatic attraction, two classes of excitons are able to be formed on both host and dopant, resulting in a dual emission and thus white EL ( Figure 4B) (Liu et al, 2005;Farmer et al, 2011;Li et al, 2014). To avoid the above-mentioned aggregation induced TTA in neat films, doped devices were further assembled with FIGURE 4 | Comparison of the EL spectra and proposed working mechanism between PCzDMPE-R5.0 (A) and D2-PCzDMPE-R5.0 (B).…”

Section: Electroluminescent Propertiesmentioning

confidence: 99%

Trap-Controlled White Electroluminescence From a Single Red-Emitting Thermally Activated Delayed Fluorescence Polymer

Yang

et al. 2020

Front. Chem.

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Single white-emitting polymers have been reported by incorporating the secondgeneration carbazole dendron into the side chain of a red-emitting thermally activated delayed fluorescence (TADF) polymer. Due to the prevented hole trap effect, in this case, excitons can be generated simultaneously on the polymeric host and the red TADF dopant to give a dual emission. Consequently, a bright white electroluminescence is achieved even at a dopant loading as high as 5 mol.%, revealing a maximum luminous efficiency of 16.1 cd/A (12.0 lm/W, 8.2%) and Commission Internationale de l'Eclairage (CIE) coordinates of (0.42, 0.32). The results clearly indicate that the delicate tuning of charge trap is a promising strategy to develop efficient single white-emitting polymers, whose low-band-gap chromophore content can be up to a centesimal level.

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Charge Transport in Amorphous Organic Semiconductors: Effects of Disorder, Carrier Density, Traps, and Scatters

Cited by 39 publications

References 78 publications

Organic Field‐Effect Transistors: A 3D Kinetic Monte Carlo Simulation of the Current Characteristics in Micrometer‐Sized Devices

Organic Field‐Effect Transistors: A 3D Kinetic Monte Carlo Simulation of the Current Characteristics in Micrometer‐Sized Devices

Force and current in a contact gap between single highly resistive particles: experimental observations

Trap-Controlled White Electroluminescence From a Single Red-Emitting Thermally Activated Delayed Fluorescence Polymer

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