Interplay of polaronic and disorder effects on electronic charge transport

Stephan, Jörg; Liemant, Alfred; Albrecht, F.; Brehmer, L.

doi:10.1016/s0379-6779(99)00255-6

Cited by 5 publications

(2 citation statements)

References 8 publications

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“…Therefore, the mobility in blends is lower than the neat mobility and the effect of blend morphology is reminiscent of off-diagonal disorder effects in neat materials. 39,40 If positional disorder is strong, the mobility of neat materials can also be negative. 39 Note that in the foregoing discussion no reference has been made to energetic disorder.…”

Section: Resultsmentioning

confidence: 99%

Charge carrier mobility in disordered organic blends for photovoltaics

Koster

2010

Phys. Rev. B

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Please check the document version of this publication:• A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal.If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User Agreement: www.tue.nl/taverne Take down policyIf you believe that this document breaches copyright please contact us at: openaccess@tue.nl providing details and we will investigate your claim. Charge transport in disordered organic blends is studied theoretically by numerically solving the Pauli master equation. The influence of morphology, disorder, electric field, and charge carrier concentration on blend mobility is assessed. Important differences between neat materials and blends are found. The dependence of mobility on charge carrier concentration is more pronounced in blends and it is influenced by the electric field strength. At low charge carrier densities, blend mobility is found to decrease with increasing field. Additionally, the impact of the volume ratio of the constituent materials and their domain size on the mobility is presented. Especially for strongly disordered materials charge transport is favored by relatively large domains. To compare these theoretical findings with existing experimental mobility data, the current density in a space-charge-limited device is computed. The author finds that, for the parameters and morphologies studied, the apparent mobility in such a device decreases with increasing bias voltage.

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Section: Resultsmentioning

confidence: 99%

Charge carrier mobility in disordered organic blends for photovoltaics

Koster

2010

Phys. Rev. B

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“…In particular, one such study has focused on the effect of spatial disorder and spatial anisotropy of a polymer film on the mobility [73], utilizing the Monte Carlo technique. Spatial disorder was introduced by randomly varying the lattice spacing, whereas anisotropy was incorporated through variations of the lattice constant perpendicular to the direction of the applied field.…”

Section: Effects Of Spatial Disordermentioning

confidence: 99%

Electrical transport modelling in organic electroluminescent devices

Walker¹,

Kambili

Martin

2002

J. Phys.: Condens. Matter

114

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Organic electroluminescent devices (OEDs) emit light when an electric current is applied to a thin film section. They arise from two main technology branches—small molecules and light emitting polymers. Apart from the insight offered into the fundamentals of their physics, which is relevant to topics such as electrical transport in biological systems and molecular computers, understanding how the mobilities in these systems vary with morphology and composition enables the design of improved materials for technological requirements, e.g. fast switching speeds for active matrix displays and polymer field effect transistors. In this review, we have focussed on the models of transport in OEDs that address the unusual nature of this transport and underpin device design. The review concludes with the following point: as new materials for use in OEDs continue to appear, modelling is essential for the prediction of their transport properties, which in turn leads to the establishment of fundamental trends in the behaviour of devices employing them.

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Kinetic Monte Carlo model of charge transport in hematite (α-Fe2O3)

Kerisit

Rosso

2007

The Journal of Chemical Physics

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The mobility of electrons injected into iron oxide minerals via abiotic and biotic electron transfer processes is one of the key factors that control the reductive dissolution of such minerals. Building upon our previous work on the computational modeling of elementary electron transfer reactions in iron oxide minerals using ab initio electronic structure calculations and parametrized molecular dynamics simulations, we have developed and implemented a kinetic Monte Carlo model of charge transport in hematite that integrates previous findings. The model aims to simulate the interplay between electron transfer processes for extended periods of time in lattices of increasing complexity. The electron transfer reactions considered here involve the IIIII valence interchange between nearest-neighbor iron atoms via a small polaron hopping mechanism. The temperature dependence and anisotropic behavior of the electrical conductivity as predicted by our model are in good agreement with experimental data on hematite single crystals. In addition, we characterize the effect of electron polaron concentration and that of a range of defects on the electron mobility. Interaction potentials between electron polarons and fixed defects (iron substitution by divalent, tetravalent, and isovalent ions and iron and oxygen vacancies) are determined from atomistic simulations, based on the same model used to derive the electron transfer parameters, and show little deviation from the Coulombic interaction energy. Integration of the interaction potentials in the kinetic Monte Carlo simulations allows the electron polaron diffusion coefficient and density and residence time around defect sites to be determined as a function of polaron concentration in the presence of repulsive and attractive defects. The decrease in diffusion coefficient with polaron concentration follows a logarithmic function up to the highest concentration considered, i.e., approximately 2% of iron(III) sites, whereas the presence of repulsive defects has a linear effect on the electron polaron diffusion. Attractive defects are found to significantly affect electron polaron diffusion at low polaron to defect ratios due to trapping on nanosecond to microsecond time scales. This work indicates that electrons can diffuse away from the initial site of interfacial electron transfer at a rate that is consistent with measured electrical conductivities, but that the presence of certain kinds of defects will severely limit the mobility of donated electrons.

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Interplay of polaronic and disorder effects on electronic charge transport

Cited by 5 publications

References 8 publications

Charge carrier mobility in disordered organic blends for photovoltaics

Charge carrier mobility in disordered organic blends for photovoltaics

Electrical transport modelling in organic electroluminescent devices

Kinetic Monte Carlo model of charge transport in hematite (α-Fe2O3)

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