Molecular-scale simulation of electroluminescence in a multilayer white organic light-emitting diode

Mesta, Murat; Carvelli, M Marco; Vries, Rein J. de; Eersel, Harm van; Holst, Jens J.; Schober, Matthias; Furno, Mauro; Lüssem, Björn; Leo, Karl; Loebl, Peter; Coehoorn, R.; Bobbert, Peter A.

doi:10.1038/nmat3622

Cited by 157 publications

(170 citation statements)

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“…[7,10], the effect of the weak spatial energy correlations on both the electron and hole mobility functions of α-NPD, TCTA, and Spiro-DPVBi [2,2',7,7'-tetrakis(2,2-diphenylvinyl)Spiro-9,9'-bifluorene]. In the latter material, which is used as a blue fluorescent emitter in OLEDs [17], both electron and hole transport are important [18].…”

Section: Introductionmentioning

confidence: 99%

“…We recently established from ab initio calculations that including superexchange coupling of guest orbitals via virtual host orbitals leads to a strong enhancement and change in the guest concentration dependence of the hole mobility in two prototypical host-guest systems often used as emitting layers in OLEDs [18]: α-NPD:Ir(MDQ)2(acac) (α-NPD doped with the red-emitting dye (acelylacetonate)bis(2-methyldibenzo[f,h]quinoxinalate)iridium) and TCTA:Ir(ppy) 3 (TCTA doped with the green-emitting dye fac-tris(2-phenylpyridyl)iridium) [22]. Although in pure α-NPD and TCTA a similarly strong enhancement of the mobility is not expected, the longer hopping range associated with superexchange is expected to enhance its F dependence.…”

Section: Introductionmentioning

confidence: 99%

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Effects of energy correlations and superexchange on charge transport and exciton formation in amorphous molecular semiconductors: An ab initio study

et al. 2017

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Massé, A.; Friederich, P.; Symalla, F.; Liu, F.; Meded, V.; Coehoorn, R.; Wenzel, W.; Bobbert, P.A. Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers)Please check the document version of this publication:• A submitted manuscript is the author's 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 Citation for published version (APA):Massé, A., Friederich, P., Symalla, F., Liu, F., Meded, V., Coehoorn, R., ... Bobbert, P. A. (2017). Effects of energy correlations and superexchange on charge transport and exciton formation in amorphous molecular semiconductors: an ab initio study. Physical Review B, 95(11), 1-11. [115204]. DOI: 10.1103/PhysRevB.95.115204 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 ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. In this study, we investigate on the basis of ab initio calculations how the morphology, molecular on-site energies, reorganization energies, and charge transfer integral distribution affect the hopping charge transport and the exciton formation process in disordered organic semiconductors. We focus on three materials applied frequently in organic light-emitting diodes: α-NPD, TCTA, and Spiro-DPVBi. Spatially correlated disorder and, more importantly, superexchange contributions to the transfer integrals, are found to give rise to a significant increase of the electric field dependence of the electron and hole mobility. Furthermore, a material-specific correlation is found between the HOMO and LUMO energy on each specific molecular site. For α-NPD and TCTA, we find a positive correlation between the HOMO and LUMO energies, dominated by a Coulombic contribution to the energies. In contrast, Spiro-DPVBi shows a negative correlation, dominated by a conformational contribution. The size and sign of this correlation have a strong...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effects of energy correlations and superexchange on charge transport and exciton formation in amorphous molecular semiconductors: An ab initio study

et al. 2017

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“…Charge carrier injection, transport, and exciton generation are treated as described in Ref. 8; Coulomb interactions and image charge effects are included. The extended model also includes exciton diffusion by both the F€ orster 9 and Dexter 10 mechanisms, radiative and non-radiative decay, exciton dissociation, and losses due to TPQ and TTA, as described further below.…”

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Monte Carlo study of efficiency roll-off of phosphorescent organic light-emitting diodes: Evidence for dominant role of triplet-polaron quenching

Eersel

Bobbert

Janssen

et al. 2014

Applied Physics Letters

102

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We present an advanced molecular-scale organic light-emitting diode (OLED) model, integrating both electronic and excitonic processes. Using this model, we can reproduce the measured efficiency roll-off for prototypical phosphorescent OLED stacks based on the green dye tris[2-phenylpyridine]iridium (Ir(ppy)3) and the red dye octaethylporphine platinum (PtOEP) and study the cause of the roll-off as function of the current density. Both the voltage versus current density characteristics and roll-off agree well with experimental data. Surprisingly, the results of the simulations lead us to conclude that, contrary to what is often assumed, not triplet-triplet annihilation but triplet-polaron quenching is the dominant mechanism causing the roll-off under realistic operating conditions. Simulations for devices with an optimized recombination profile, achieved by carefully tuning the dye trap depth, show that it will be possible to fabricate OLEDs with a drastically reduced roll-off. It is envisaged that J90, the current density at which the efficiency is reduced to 90%, can be increased by almost one order of magnitude as compared to the experimental state-of-the-art.

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“…Theoretical and computational models have therefore proven valuable in rationalizing material and device properties, using, for example, top-down approaches such as Gaussian disorder or drift-diffusion models tailored to the description of charge and energy transport [19,20,44,45]. These mesoscopic models 1.3.…”

Section: Chapter 1 Organic Electronics In a Nutshellmentioning

confidence: 99%

The (Non-)Local Density of States of Electronic Excitations in Organic Semiconductors

Poelking

2018

Springer Theses

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The (Non-)Local Density of States of Electronic Excitations in Organic Semiconductors The rational design of organic semiconductors for optoelectronic devices relies on a detailed understanding of how their molecular and morphological structure condition the energetics and dynamics of charged and excitonic states. Investigating the role of molecular architecture, conformation, orientation and packing, this work reveals mechanisms that shape the spatially resolved densities of states in organic, small-molecular and polymeric heterostructures and mesophases. The underlying computational framework combines multiscale simulations of the material morphology at atomistic and coarse-grained resolution with a long-range-polarized embedding technique to resolve the electronic structure of the molecular solid. We show that longrange electrostatic interactions tie the energetics of microscopic states to the mesoscopic structure, with a qualitative and quantitative impact on charge-carrier level profiles across organic interfaces. The computational approach provides quantitative access to the charge-density-dependent opencircuit voltage of planar heterojunctions. The derived and experimentally verified relationships between molecular orientation, architecture, level profiles and open-circuit voltage rationalize the acceptor-donor-acceptor pattern for donor materials in high-performing solar cells. Proposing a pathway for barrier-less dissociation of charge transfer states, we highlight how mesoscale fields generate charge splitting and detrapping forces in systems with finite interface roughness. The associated design rules reflect the dominant role played by lowest-energy configurations at the interface. Acknowledgements 121 Die (nicht-)lokale Zustandsdichte elektronischer Anregungen in organischen Halbleitern List of Publications 123Bibliography 125 Chapter 1 Organic Electronics in a NutshellThe discovery of conductive polymers in the 1970s [1,2] -rewarded with the Nobel prize in chemistry in the year 2000 -and subsequent development of the first polymeric electronic devices in the 1980s [3-5] have marked the beginnings of a vast interdisciplinary research field referred to as organic electronics. Drawing from both polymeric and small-molecular semiconductors, organic thin-film transistors, solar cells, light-emitting diodes, photodetectors and sensors name just a few out of many applications that make use of the supreme chemical versatility and mechanical flexibility of the underlying "soft" molecular materials. Furthermore enabling low-temperature solution-based processing, printing and spray coating, organic electronics is set to complement the conventional silicon-based electronics in diverse waysadding functionality and improving sustainability. This introductory chapter will provide a short review of the materials and device physics, as well as of new trends and challenges that emerged in the field over the past decade. MaterialsOrganic semiconductors are molecular materials that exist at the interface between orga...

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Molecular-scale simulation of electroluminescence in a multilayer white organic light-emitting diode

Cited by 157 publications

References 34 publications

Effects of energy correlations and superexchange on charge transport and exciton formation in amorphous molecular semiconductors: An ab initio study

Effects of energy correlations and superexchange on charge transport and exciton formation in amorphous molecular semiconductors: An ab initio study

Monte Carlo study of efficiency roll-off of phosphorescent organic light-emitting diodes: Evidence for dominant role of triplet-polaron quenching

The (Non-)Local Density of States of Electronic Excitations in Organic Semiconductors

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