Modeling of Organic Light Emitting Diodes: From Molecular to Device Properties

Kordt, Pascal; Holst, Jeroen J. M. van der; Helwi, Mustapha Al; Kowalsky, Wolfgang; May, Falk; Badinski, A.; Lennartz, Christian; Andrienko, Denis

doi:10.1002/adfm.201403004

Cited by 146 publications

(161 citation statements)

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“…densities of states from first principles, and ultimately to establish their connection to device characteristics [18,28,50,[97][98][99]. In Sec.…”

Section: Chapter 3 the Local Density Of Statesmentioning

confidence: 99%

Section: Chapter 3 the Local Density Of Statesmentioning

confidence: 99%

“…Today's stack architectures consist of multiple layers (see ITO [26]. (b) Stack of a blue phosphorescent BTDF:TBFMI OLED [28]. Doped layers are indicated by a star * .…”

Section: Devicesmentioning

confidence: 99%

“…2.3.1), the sensitive relationship between dynamics and energetics controls, for example, charge-carrier mobilities, short-circuit currents, open-circuit voltages or material wearout. It is therefore a key challenge in computational materials science to predict these densities of states from first principles, and ultimately to establish their connection to device characteristics [18,28,50,[97][98][99]. In Sec.…”

Section: The Mesoscopic Interaction Rangementioning

confidence: 99%

“…As a quantitative treatment usually requires an atomistic resolution, system sizes addressed in today's simulations may in particular prove insufficient to sample the tail of the densities of states, which determines the charge-carrier mobility. Possible solutions to some of these finite-size effects include statistical extrapolation techniques [28] or coarse-grained descriptions with reinsertion of atomistic details [72].Still, the need to go beyond the local molecular ordering associated with a length scale of some nanometers is not only due to sampling requirements: It is additionally motivated by the fact that organic semiconductors are made of quadrupolar building blocks [104,105], which give rise to an uncompensated quadrupole moment that in ordered systems extends to the mesoscale and beyond. For computations, this complicates matters, as the interaction of a charge with a 3D-periodic net-quadrupolar environment is only conditionally convergent [106].…”

mentioning

confidence: 99%

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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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“…densities of states from first principles, and ultimately to establish their connection to device characteristics [18,28,50,[97][98][99]. In Sec.…”

Section: Chapter 3 the Local Density Of Statesmentioning

confidence: 99%

Section: Chapter 3 the Local Density Of Statesmentioning

confidence: 99%

“…Today's stack architectures consist of multiple layers (see ITO [26]. (b) Stack of a blue phosphorescent BTDF:TBFMI OLED [28]. Doped layers are indicated by a star * .…”

Section: Devicesmentioning

confidence: 99%

Section: The Mesoscopic Interaction Rangementioning

confidence: 99%

mentioning

confidence: 99%

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

Poelking

2018

Springer Theses

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Molecular Origin of the Charge Carrier Mobility in Small Molecule Organic Semiconductors

Friederich

Meded

Poschlad

et al. 2016

Adv Funct Materials

108

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Future prospects of the organic light emitting diode (OLED) technology rely on the development of new organic semiconductors with optical and electronic properties outperforming those of presently available materials. Computational materials design is becoming a widely used tool to complement and accelerate experimental efforts. Computational tools were also shown to contribute to the understanding of experimentally observed phenomena. Impurities and charge traps are omnipresent in most currently available organic semiconductors and limit the charge transport and thus the efficiency of the devices. The microscopic cause as well as the chemical nature of these traps is presently not well understood. Using a multiscale model we characterize the influence of impurities on the density of states and charge transport in small-molecule amorphous organic semiconductors. We use the model to quantitatively describe the influence of water molecules and water-oxygen complexes on the electron and hole mobility by influencing the shape of the density of states and at the same time acting as explicit charge traps within the energy gap. Our results show that deep trap states introduced by molecular oxygen mainly determine the electron mobility in widely used materials such as α-NPD. TOC

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Resolving Donor–Acceptor Interfaces and Charge Carrier Energy Levels of Organic Semiconductors with Polar Side Chains

Alessandri

Sami

Barnoud

et al. 2020

Adv Funct Materials

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Organic semiconductors consisting of molecules bearing polar side chains have been proposed as potential candidates to overcome the limitations of organic photovoltaics owing to their enhanced dielectric constant. However, introducing such polar molecules in photovoltaic devices has not yet resulted in higher efficiencies. A microscopic understanding of the impact of polar side chains on electronic and structural properties of organic semiconductors is paramount to rationalize their effect. Here, the impact of such side chains on bulk heterojunction overall morphology, molecular configurations at donor-acceptor (DA) interfaces, and charge carrier energy levels is investigated. The multiscale modeling approach used allows to resolve DA interfaces with atomistic resolution while taking into account the large-scale self-organization process which takes place during the processing of an organic thin film. The polar fullerene-based blends are compared to the well-studied reference system, poly(3-hexyl-thiophene) (P3HT):phenyl-C 61butyric acid methyl ester (PCBM). Introduction of polar side chains on a similar molecular scaffold does not affect molecular orientations at the DA interfaces; such orientations are, however, found to be affected by processing conditions and polymer molecular weight. Polar side chains, instead, are found to impact considerably the charge carrier energy levels of the organic blend, causing electrostatic-induced broadening of these levels.

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Modeling of Organic Light Emitting Diodes: From Molecular to Device Properties

Cited by 146 publications

References 157 publications

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

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

Molecular Origin of the Charge Carrier Mobility in Small Molecule Organic Semiconductors

Resolving Donor–Acceptor Interfaces and Charge Carrier Energy Levels of Organic Semiconductors with Polar Side Chains

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