Current–voltage characteristics of dendrimer light-emitting diodes

Stevenson, Stuart G.; Samuel, Ifor D. W.; Staton, S.V.; Knights, Kevin A.; Burn, Paul L.; Williams, J H T; Walker, Alison B.

doi:10.1088/0022-3727/43/38/385106

Cited by 4 publications

(3 citation statements)

References 30 publications

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“…However, later work has suggested that injection barriers may commonly exist in metal-organic interfaces that are normally assumed to be ohmic, 6 and other modeling work has reached the same conclusion. 52 This may account for the necessity of including injection barriers in the KMC model, especially as it includes an explicit hopping description between discrete energy levels, which is not included in drift-diffusion modeling.…”

Section: Resultsmentioning

confidence: 99%

Mesoscopic kinetic Monte Carlo modeling of organic photovoltaic device characteristics

et al. 2012

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Measured mobility and current-voltage characteristics of single layer and photovoltaic (PV) devices composed of poly{9,9-dioctylfluorene-co-bis[N,N -(4-butylphenyl)]bis(N,N -phenyl-1,4-phenylene)diamine} (PFB) and poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) have been reproduced by a mesoscopic model employing the kinetic Monte Carlo (KMC) approach. Our aim is to show how to avoid the uncertainties common in electrical transport models arising from the need to fit a large number of parameters when little information is available, for example, a single current-voltage curve. Here, simulation parameters are derived from a series of measurements using a self-consistent "building-blocks" approach, starting from data on the simplest systems. We found that site energies show disorder and that correlations in the site energies and a distribution of deep traps must be included in order to reproduce measured charge mobility-field curves at low charge densities in bulk PFB and F8BT. The parameter set from the mobility-field curves reproduces the unipolar current in single layers of PFB and F8BT and allows us to deduce charge injection barriers. Finally, by combining these disorder descriptions and injection barriers with an optical model, the external quantum efficiency and current densities of blend and bilayer organic PV devices can be successfully reproduced across a voltage range encompassing reverse and forward bias, with the recombination rate the only parameter to be fitted, found to be 1 × 10 7 s −1 . These findings demonstrate an approach that removes some of the arbitrariness present in transport models of organic devices, which validates the KMC as an accurate description of organic optoelectronic systems, and provides information on the microscopic origins of the device behavior.

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Section: Resultsmentioning

confidence: 99%

Mesoscopic kinetic Monte Carlo modeling of organic photovoltaic device characteristics

et al. 2012

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“…Although much of the context for this analysis has concerned dendrimeric systems acting as solar energy harvesters, there are several other important and emerging areas of application deserving mention, including molecular sensing [104][105][106], catalysis [104,107], medical photonics [104,108] and light-emitting diodes [109][110][111]. Most uses exploit the following generic properties: the possession of a multiplicity of chromophores that are responsible for initial photon absorption, and which can also act as relays; these groups display broad and intense absorption bands, and correspondingly strong emission bands; RET mechanisms are in place for the efficient transmission of electronic excitation by a sequence of transfers, providing a means for the direct routing of each excitation from peripheral to core chromophores; irreversibility of energy capture is achieved through intramolecular relaxation (energy losses) at each intervening site.…”

Section: Discussionmentioning

confidence: 99%

Mechanisms of Light Energy Harvesting in Dendrimers and Hyperbranched Polymers

Bradshaw

Andrews

2011

Polymers

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Abstract:Since their earliest synthesis, much interest has arisen in the use of dendritic and structurally allied forms of polymer for light energy harvesting, especially as organic adjuncts for solar energy devices. With the facility to accommodate a proliferation of antenna chromophores, such materials can capture and channel light energy with a high degree of efficiency, each polymer unit potentially delivering the energy of one photon-or more, when optical nonlinearity is involved. To ensure the highest efficiency of operation, it is essential to understand the processes responsible for photon capture and channelling of the resulting electronic excitation. Highlighting the latest theoretical advances, this paper reviews the principal mechanisms, which prove to involve a complex interplay of structural, spectroscopic and electrodynamic properties. Designing materials with the capacity to capture and control light energy facilitates applications that now extend from solar energy to medical photonics.

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“…Conventional device models adapted from inorganic device simulation have given strong insights into OLED behavior at macroscopic length scalesVfor recent examples, see [38] and [39]Vand they have been reviewed along with the GDM in [40]. The hopping nature of conduction in organic materials discussed in Section II is taken into account by the use of field-dependent charge mobilities obtained from experiment.…”

Section: Device Modelsmentioning

confidence: 99%

Multiscale Modeling of Charge and Energy Transport in Organic Light-Emitting Diodes and Photovoltaics

Walker

2009

Proc. IEEE

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| Modelling organic devices is an outstanding challenge because device performance is very sensitive to how the molecules are packed and the films are highly disordered. An understanding of charge and exciton (bound electron-hole pair) transport in these materials is important if organic light-emitting diodes are to be exploited in displays, lighting, photovoltaics, transistors, and sensors. This paper discusses methods we have pioneered for predicting charge and exciton transport, in which polymer chains are explicitly modeled and charge and exciton transfer rates are taken from electronic structure theory. Monte Carlo and drift diffusion device models that link device performance with morphology are also covered. The focus here is on polymers, but there is much in common with small molecule organic materials.A good summary of organic light-emitting diode (OLED) technology can be found at http://www.en.wikipedia.org. For up-to-date information about applications and many excellent technical reviews, consult Web sites such as www.oled-info.com, www.idtechex.com, and those of the firms exploiting this technology.

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Current–voltage characteristics of dendrimer light-emitting diodes

Cited by 4 publications

References 30 publications

Mesoscopic kinetic Monte Carlo modeling of organic photovoltaic device characteristics

Mesoscopic kinetic Monte Carlo modeling of organic photovoltaic device characteristics

Mechanisms of Light Energy Harvesting in Dendrimers and Hyperbranched Polymers

Multiscale Modeling of Charge and Energy Transport in Organic Light-Emitting Diodes and Photovoltaics

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