The mobility in disordered molecular systems with energies given by a charge-induced dipoles interaction

Tonezer, Camila; Freire, José A.

doi:10.1063/1.3512633

Cited by 9 publications

(22 citation statements)

References 15 publications

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“…Here we apply the model of Tonezer and Freire24 to our TOF mobility measurements. The model is based on Gaussian distribution of DOS, where the only source of the hopping site energies is given by the interaction of the charge in the site with the surrounding induced dipoles (short‐range correlation).…”

Section: Resultsmentioning

confidence: 99%

“…We explore this by measuring the temperature and field dependence of the hole mobility, using the charge‐generation layer time‐of‐flight (TOF) technique ( Figure inset), for the doubly dendronised iridium(III) complex. Furthermore we analyze the experimental results within the Gaussian disorder model (GDM),21 correlated disorder model (CDM),22 polaronic correlated disorder model (polaronic CDM),23 and short range correlated Gaussian disorder model (short CDM) 24…”

Section: Introductionmentioning

confidence: 99%

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Charge Transport in a Highly Phosphorescent Iridium(III) Complex‐Cored Dendrimer with Double Dendrons

Gambino

Liu

et al. 2011

Adv Funct Materials

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The charge transporting properties of a phosphorescent iridium(III) complexcored dendrimer, with two dendrons attached to each ligand of the core are reported. The results show that the high photoluminescence quantum yield of this material is obtained without compromising charge transport. The hole mobility values are reported over a wide range of temperatures and electric fields using the charge-generation layer time-of-flight technique. The results are analysed using the Gaussian disorder model (GDM), the correlated disorder model, the polaronic correlated disorder model, and the short-range correlated Gaussian disorder model. It is found that the GDM model gives the most comprehensive description of hole transport in this material. In spite of its larger size, the hole mobility of the doubly dendronised material compares favourably with that of a smaller singly dendronised material, and its spherical shape leads to low energetic disorder and clearly non-dispersive charge transport. This shows how molecular shape can be used to combine favourable photoluminescence and charge-transporting properties.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Charge Transport in a Highly Phosphorescent Iridium(III) Complex‐Cored Dendrimer with Double Dendrons

Gambino

Liu

et al. 2011

Adv Funct Materials

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“…The strong correlation of the site energy in an ensemble of uncorrelated dipoles has its origin in the long-range nature of the dipole electrostatic potential. The fall-off with distance is faster for lower dimensions -for a 2D lattice, f (r) ∼ 1∕r 3 and for a 1D lattice, f (r) ∼ (log r)∕r 3 [107] -and for the case of a charge interacting with induced dipoles (instead of permanent ones) [21,108]. The energy landscape that results when correlations are included can be considered as one in which a larger-scale variation of the potential energy superimposes on small local site energy fluctuations.…”

Section: Disorder-controlled Transportmentioning

confidence: 99%

Electronic and Optical Processes of Organic Semiconductors

Köhler

Bäßler

2015

Electronic Processes in Organic Semiconductors

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Semiconductors are, by definition, materials that are intended for use in optoelectronic devices. The most common applications of organic semiconductors encompass organic light-emitting diodes (OLEDs), organic solar cells (OSCs), and organic field-effect transistors (OFETs) (Figure 3.1).In essence, an OLED is made in a sandwich-type structure by covering a substrate sequentially with a bottom electrode, the active semiconducting material and a top electrode. Upon applying a voltage, positive and negative charges are injected from the electrodes into the semiconductor and move through it. While a part of these charges may leave the organic film at the counter electrode, having resulted in nothing but dissipated heat, some of the electrons and holes will encounter and capture each other to form an excited state that may recombine with or without light emission. The processes involved in the operation of an OLED are illustrated in Figure 3.1, along with the processes relevant for an OSC. The OSC has, in principle, the same structure as that of an OLED; yet, it operates in the reverse direction. Light is absorbed and creates excited states. Some of these states may eventually dissociate into free, mobile positive and negative charges that move to opposite electrodes where they are collected to yield a current. The photophysical mechanisms associated with OLEDs and OSC operation, such as charge injection, charge transport, electron-hole recombination, and excited state dissociation are discussed in detail in the corresponding sections of this chapter. Also included are processes relating to the excited states such as energy transfer and decay mechanisms. Issues pertaining to the fabrication, operation, characterization, and optimization of the entire device are considered in the next chapter. The same approach of chapter organization is taken concerning the OFET. The fabrication and operation of the OFET is detailed in Chapter 4, whereas this chapter covers, inter alia, the process of charge transport for the regimes of low and high charge carrier density.The generic structure of an OFET differs from the OLED/OSC structure. An OFET contains three electrodes in contrast to the two electrodes of the OLED/OSC layout. In the OFET, two electrodes, the source and the drain electrode, are separated by the active semiconductor. When a voltage is applied between the source and the drain electrode, current can, in principle, flow between them. The amount of current that flows is controlled by the third, the gate electrode that is separated from the active semiconductor by an insulator layer. If there is no voltage applied to the gate electrode, the current flow between the source and the drain is negligibly small, even when there is a potential difference between the source and the drain. The reason for this lies in the high resistivity of the organic semiconductor in combination with the device geometry. In an OLED, the electrodes are separated only by 100 nm of semiconductor, and the electrodes cover most of the semiconductor...

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“…Sometimes in the literature one can find a statement that short range correlations are quite sufficient for the development of the field dependence which is almost indistinguishable from the true PF dependence in a wide field range and, hence, for a description of transport properties of organic materials (a recent example is provided in Ref. 50) In order to understand the importance of long range correlations it is useful to compare our Fig. 1 (inset) and Fig.…”

Section: A Mobility Field Dependencementioning

confidence: 99%

“…50; for E = 5 V/µm in our case (eaE/σ) 1/2 = 0.163 and for the reference mobility value for data from Ref. 50 we used, instead of µ5, the mobility, simulated for the same value of (eaE/σ) 1/2 .…”

Section: A Mobility Field Dependencementioning

confidence: 99%

Charge carrier transport in molecularly doped polycarbonate as a test case for the dipolar glass model

Новиков

Tyutnev

2013

The Journal of Chemical Physics

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We present the results of Monte-Carlo simulations of the charge carrier transport in a disordered molecular system containing spatial and energetic disorders using the dipolar glass model. Model parameters of the material were chosen to fit a typical polar organic photoconductor polycarbonate doped with 30% of aromatic hydrazone, whose transport properties are well documented in literature. Simulated carrier mobility demonstrates a usual Poole-Frenkel field dependence and its slope is very close to the experimental value without using any adjustable parameter. At room temperature transients are universal with respect to the electric field and transport layer thickness. At the same time, carrier mobility does not depend on the layer thickness and transients develop a well-defined plateau where the current does not depend on time, thus demonstrating a non-dispersive transport regime. Tails of the transients decay as power law with the exponent close to -2. This particular feature indicates that transients are close to the boundary between dispersive and non-dispersive transport regimes. Shapes of the simulated transients are in very good agreement with the experimental ones. In summary, we provide a first verification of a self-consistency of the dipolar glass transport model, where major transport parameters, extracted from the experimental transport data, are then used in the transport simulation, and the resulting mobility field dependence and transients are in very good agreement with the initial experimental data.

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The mobility in disordered molecular systems with energies given by a charge-induced dipoles interaction

Cited by 9 publications

References 15 publications

Charge Transport in a Highly Phosphorescent Iridium(III) Complex‐Cored Dendrimer with Double Dendrons

Charge Transport in a Highly Phosphorescent Iridium(III) Complex‐Cored Dendrimer with Double Dendrons

Electronic and Optical Processes of Organic Semiconductors

Charge carrier transport in molecularly doped polycarbonate as a test case for the dipolar glass model

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