Charge transport in disordered organic solids: A Monte Carlo simulation study on the effects of film morphology

Mohan, S. Raj; Joshi, M. P.; Singh, Manjeet

doi:10.1016/j.orgel.2007.12.005

Cited by 19 publications

(28 citation statements)

References 36 publications

(56 reference statements)

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“…However, as previously noted from Figure 3(a) the response of σ GDM is not as sensitive as σ DOS to the introduction of local order where it is typically found that to achieve a 50% reduction in σ GDM relative to the DG reference magnitude it is necessary for C to exceed about 0.9 for n/N > 0.3. Similar behaviour has been reported in independent Monte Carlo studies [13][14][15] which was attributed to weakly percolating transport where the majority of carriers follow low-mobility paths through NOC sites. The preference to hop via the NOC sites is clearly understood with reference to Figure 4 where it is noted that after the injected carriers have had an opportunity to thermalise they will tend to occupy the lowest energy states associated with the σ DOS (NOC) tail.…”

Section: Simulation Of Dipolar Glassessupporting

confidence: 86%

“…Simulations with local ordering have been performed to model both DGs and MDPs. This work extends independent previous Monte Carlo studies which have either considered short-range order in MDPs using non-correlated random orientation vectors [12], or have examined the effect of introducing ordered regions into DG energy landscapes by using pre-determined Gaussian distributions to perform the allocation of site energies [13][14][15]. By contrast the generation of energy landscapes in the present study has been achieved using a fundamental electrostatic calculation of the dipole potential, where local variations of the potential have been introduced using dipoles that are locally ordered within cubic regions that have a specified volume.…”

Section: Introductionmentioning

confidence: 63%

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The Sensitivity of Hopping Transport in Dipolar Glasses and Molecularly Doped Polymers to Localised Dipole Ordering

Goldie¹

2012

MATERIALS

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The influence of ordered dipole regions upon hopping transport through dipolar glasses and molecularly doped polymers has been evaluated via Monte Carlo simulation. Ordered dipole regions were introduced as a set of randomly distributed cubes throughout disordered dipolar lattices where the number and size of the cubes could be independently varied. Within each cube neighbouring dipoles were anti-aligned to minimise the local energetic disorder but the specific dipole orientation for each inserted cube was randomly selected. Whilst the underlying density of states appears to become energetically narrower as the overall proportion of disordered dipole sites is diluted by inserted ordered cubes this is not generally reflected in the associated transport properties. It is demonstrated that the lattice potential that is associated with background non-aligned dipoles in dipolar glasses have a controlling influence upon the observed macroscopic mobility. Confirmation of the importance of such non-aligned dipoles is provided by complimentary simulations using molecularly doped polymers where the dopant dipoles are agglomerated and ordered into cubic regions. The implication of the simulation results for the interpretation of experimental transport data in dipolar glasses and molecularly doped polymers is evaluated.

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Section: Simulation Of Dipolar Glassessupporting

confidence: 86%

Section: Introductionmentioning

confidence: 63%

The Sensitivity of Hopping Transport in Dipolar Glasses and Molecularly Doped Polymers to Localised Dipole Ordering

Goldie¹

2012

MATERIALS

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“…The influence of film morphology on optical and electrical properties has been investigated extensively as this understanding is indispensable for the design and development of efficient organic optoelectronic devices [25][26][27][28][29][30][31][32] . One of the prime motives behind tailoring the film morphology is to incorporate more structural order in an otherwise highly disordered homogeneous system for providing percolation pathways and thereby enhancing the charge carrier mobility [25][26][27][28] .…”

Section: Introductionmentioning

confidence: 99%

“…One of the prime motives behind tailoring the film morphology is to incorporate more structural order in an otherwise highly disordered homogeneous system for providing percolation pathways and thereby enhancing the charge carrier mobility [25][26][27][28] . These morphologically tailored films contain a blend of ordered regions and disordered regions, where the energetic disorder is low and high respectively [25][26][27][28][29][30][31][32] . Hence, these morphologically tailored films cannot be treated as homogeneous rather they are inhomogeneous [25][26][27][28][29][30][31][32] .…”

Section: Introductionmentioning

confidence: 99%

“…These morphologically tailored films contain a blend of ordered regions and disordered regions, where the energetic disorder is low and high respectively [25][26][27][28][29][30][31][32] . Hence, these morphologically tailored films cannot be treated as homogeneous rather they are inhomogeneous [25][26][27][28][29][30][31][32] . The charge transport in such system occurs through a mixture of ordered and less ordered regions.…”

Section: Introductionmentioning

confidence: 99%

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Monte Carlo Simulation of Carrier Diffusion in Organic Thin Films with Morphological Inhomogeneity

et al. 2013

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Monte Carlo simulation was carried out to understand the influence of morphological inhomogeneity on carrier diffusion in organic thin films. The morphological inhomogeneity was considered in the simulation by incorporating the regions of low energetic disorder in a host lattice of high energetic disorder which decreases the overall energetic disorder of the system.For the homogeneous films, the carrier diffusion was found to decrease upon decreasing the energetic disorder. In contrast to this, in the case of inhomogeneous films the carrier diffusion enhanced upon decreasing the overall energetic disorder, up to an optimum value and beyond which the carrier diffusion decreased. Through our simulation, we observed that the behavior of carrier diffusion in the inhomogeneous case is due to the morphology dependent carrier spreading, which acts in addition to the thermal and non-thermal field assisted diffusion mechanisms. This morphological dependence of carrier spreading arises due to the generation of packets of carriers with different jump rates, which is after effect of slow relaxation of the carriers generated in the less disordered regions of inhomogeneous system. Our simulation of morphology dependent carrier spreading and its influence on the basic diffusion process provide deeper insight into the charge transport mechanisms in organic thin films.

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Charge transport properties of MDMO PPV thin films cast in different solvents

Mohan

Joshi

Shalu

et al. 2015

J Polym Sci B Polym Phys

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Charge transport properties in thin films of Poly(2‐methoxy‐5‐(3′,7′‐dimethyloctyloxy)‐1,4‐phenylenevinylene) (MDMO PPV) cast using either chloroform (CF), toluene (TOL), or chlorobenzene (CB) as solvent were investigated. Hole mobility (μ) in these thin films measured using time‐of‐flight transient photoconductivity showed an increasing trend with respect to the solvent used in the same order, that is, μCF (2.4 × 10−7 cm2/Vs) < μTOL (6.9 × 10−7 cm2/Vs) < μCB (2.3 × 10−6 cm2/Vs). Observed variations in mobilities were attributed to different morphologies of MDMO PPV chains in thin films cast using the aforesaid solvents. Nature of the interchain interactions and aggregate formation were obtained using photoluminescence (PL), Raman spectroscopy, and AFM studies. Ratio of PL peak intensities of 0–0 and 0–1 transitions, which is a direct measure of interchain interaction, was the highest in CB and lowest in CF. Variation in the relative intensities of out‐of‐plane wagging of vinylene group (∼963 cm−1 mode) in Raman spectra suggested different extent of coiling of polymer chains in these thin films. From these observations, it was elicited that aggregate size and interchain interactions are highest in CB and least in CF. AFM‐based topographic images of thin films further supported these variations in the size of aggregates. Variation in the aggregate sizes and interchain interactions explained the corresponding variation in the mobility. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 1431–1439

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Charge transport in disordered organic solids: A Monte Carlo simulation study on the effects of film morphology

Cited by 19 publications

References 36 publications

The Sensitivity of Hopping Transport in Dipolar Glasses and Molecularly Doped Polymers to Localised Dipole Ordering

The Sensitivity of Hopping Transport in Dipolar Glasses and Molecularly Doped Polymers to Localised Dipole Ordering

Monte Carlo Simulation of Carrier Diffusion in Organic Thin Films with Morphological Inhomogeneity

Charge transport properties of MDMO PPV thin films cast in different solvents

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