Charge Transport in Organic Crystals: Role of Disorder and Topological Connectivity

Vehoff, Thorsten; Baumeier, Björn; Troisi, Alessandro; Andrienko, Denis

doi:10.1021/ja104380c

Cited by 168 publications

(180 citation statements)

References 54 publications

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“…Simulations are performed using the VOTCA package. 17,18 This approach has been used to calculate mobility in columnar discotic mesophases, 19−24 amorphous systems, 25−28 selfassembled monoloayers, 29 and conjugated polymers. 30,31 An amorphous morphology of 4096 BTDF molecules is obtained by first annealing the system at 700 K, well above the glass transition temperature, T g = 380 K, followed by fast quenching to room temperature.…”

Section: Resultsmentioning

confidence: 99%

Design Rules for Charge-Transport Efficient Host Materials for Phosphorescent Organic Light-Emitting Diodes

et al. 2012

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The use of blue phosphorescent emitters in organic light-emitting diodes (OLEDs) imposes demanding requirements on a host material. Among these are large triplet energies, the alignment of levels with respect to the emitter, the ability to form and sustain amorphous order, material processability, and an adequate charge carrier mobility. A possible design strategy is to choose a π-conjugated core with a high triplet level and to fulfill the other requirements by using suitable substituents. Bulky substituents, however, induce large spatial separations between conjugated cores, can substantially reduce intermolecular electronic couplings, and decrease the charge mobility of the host. In this work we analyze charge transport in amorphous 2,8-bis(triphenylsilyl)dibenzofuran, an electron-transporting material synthesized to serve as a host in deep-blue OLEDs. We show that mesomeric effects delocalize the frontier orbitals over the substituents recovering strong electronic couplings and lowering reorganization energies, especially for electrons, while keeping energetic disorder small. Admittance spectroscopy measurements reveal that the material has indeed a high electron mobility and a small Poole−Frenkel slope, supporting our conclusions. By linking electronic structure, molecular packing, and mobility, we provide a pathway to the rational design of hosts with high charge mobilities.

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Section: Resultsmentioning

confidence: 99%

Design Rules for Charge-Transport Efficient Host Materials for Phosphorescent Organic Light-Emitting Diodes

et al. 2012

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“…In general, calculated mobility values are often more accurate in small molecule systems where transfer integrals are averaged over, or an initial configuration is assumed [141,149,150]. Otherwise, these computational methods tend to overpredict the time-of-flight mobilities of material systems by two to six orders of magnitude, with more noticeable discrepancies for larger or more complex molecules with a greater quantity of physical conformations, such as polymer chains [75,80,151,152].…”

Section: Charge Mobilitymentioning

confidence: 99%

Computationally connecting organic photovoltaic performance to atomistic arrangements and bulk morphology

Jones

Jankowski

2017

Molecular Simulation

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Rationally designing roll-to-roll printed organic photovoltaics requires a fundamental understanding of active layer morphologies optimized for charge separation and transport, and which ingredients can be used to self-assemble those morphologies. In this review article we discuss advances in three areas of computational modeling that provide insight into active layer morphology and the charge transport properties that result. We explain the computational bottlenecks prohibiting atomistically-detailed simulations of device-scale active layers and the coarse-graining and hardware acceleration strategies for overcoming them. We review coarse-grained simulations of organic photovoltaic active layers and show that high throughput simulations of experimentally-relevant length scales are now accessible. We describe a new Python package diffractometer that permits grazing-incidence X-ray scattering patterns of simulated active layers to be compared against experiments. We explain the accurate calculation of charge-carrier mobilities from coarse-grained active layer morphologies by using atomistic backmapping, quantum chemical calculations, and kinetic Monte Carlo simulations. We employ these simulations to show that ordering of poly(3-hexylthiophene-2,5-diyl) explains a factor of 1000 improvement in charge mobility. In concert, we present a suite of computational tools enabling large-scale electronic properties of organic photovoltaics to be studied and screened for by molecular simulations.

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“…Work in this group and others has proposed a view of charge transport based in network analysis (5)(6)(7)(8)(9)(10). Network analysis represents a powerful means of analyzing structurally disordered charge transport networks, with the unique ability to place different mechanisms of charge transport on the same footing via the selection of a suitable graph metric.…”

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confidence: 99%

Charge transport network dynamics in molecular aggregates

Jackson

Chen

Ratner

2016

Proc. Natl. Acad. Sci. U.S.A.

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Due to the nonperiodic nature of charge transport in disordered systems, generating insight into static charge transport networks, as well as analyzing the network dynamics, can be challenging. Here, we apply time-dependent network analysis to scrutinize the charge transport networks of two representative molecular semiconductors: a rigid n-type molecule, perylenediimide, and a flexible p-type molecule, bBDT(TDPP) 2 . Simulations reveal the relevant timescale for local transfer integral decorrelation to be ∼ 100 fs, which is shown to be faster than that of a crystalline morphology of the same molecule. Using a simple graph metric, global network changes are observed over timescales competitive with charge carrier lifetimes. These insights demonstrate that static charge transport networks are qualitatively inadequate, whereas average networks often overestimate network connectivity. Finally, a simple methodology for tracking dynamic charge transport properties is proposed.organic semiconductors | charge transport | network analysis | dynamic disorder | molecular semiconductors C omputational tools using periodic boundary conditions are integral to understanding charge and excitation transport in crystalline semiconducting materials (1, 2). In noncrystalline systems, where Bloch's theorem is inapplicable and inclusion of structural disorder is required for an accurate description of charge transport, comparable computational strategies are rare. Typically, one uses an approximate solution of the master equation with semiclassical rates derived from a combination of atomistic molecular dynamics (MD) and quantum chemistry. While this strategy has proven effective (3, 4), it possesses obvious deficiencies: it lacks both an explicit inclusion of structural dynamics and an understanding of the topology of charge transport networks.Work in this group and others has proposed a view of charge transport based in network analysis (5-10). Network analysis represents a powerful means of analyzing structurally disordered charge transport networks, with the unique ability to place different mechanisms of charge transport on the same footing via the selection of a suitable graph metric. Recently, network views of charge transport in structurally disordered systems have provided useful insights: notably, the relationship between a molecule's topology and the percolation threshold of its charge transport networks (5, 6), and that charge mobility can be independent of the global morphology, being primarily determined by local molecular packing (7).Although a useful framework, previous applications of network analysis to structurally disordered charge transport networks have neglected the role of dynamic structural disorder: static snapshots of the charge transport network were used for the network analysis. Transport was assumed to occur on a charge transport network defined by time-independent site energies and electronic couplings. Whereas the static picture provides many insights into the nature of charge transport in soft mater...

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Charge Transport in Organic Crystals: Role of Disorder and Topological Connectivity

Cited by 168 publications

References 54 publications

Design Rules for Charge-Transport Efficient Host Materials for Phosphorescent Organic Light-Emitting Diodes

Design Rules for Charge-Transport Efficient Host Materials for Phosphorescent Organic Light-Emitting Diodes

Computationally connecting organic photovoltaic performance to atomistic arrangements and bulk morphology

Charge transport network dynamics in molecular aggregates

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