Link between hopping models and percolation scaling laws for charge transport in mixtures of small molecules

Mixed host compositions that combine charge transport materials with luminescent dyes offer superior control over exciton formation and charge transport in organic light emitting devices (OLEDs). Two approaches are typically used to optimize the fraction of charge transport materials in a mixed host...

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Bibliographic Details
Published in:AIP advances 2016-04, Vol.6 (4), p.045221-045221-5
Main Authors: Ha, Dong-Gwang, Kim, Jang-Joo, Baldo, Marc A.
Format: Article
Language:English
Subjects:
Benzene
blends
Charge materials
Charge transport
charged excitons
Composition
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
conduction
Conductors
current density
Empirical analysis
hole transport
hopping transport
host
mobility
n-vinylcarbazole
Organic light emitting diodes
Percolation
Scaling laws
systems
threshold
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Summary:Mixed host compositions that combine charge transport materials with luminescent dyes offer superior control over exciton formation and charge transport in organic light emitting devices (OLEDs). Two approaches are typically used to optimize the fraction of charge transport materials in a mixed host composition: either an empirical percolative model, or a hopping transport model. We show that these two commonly-employed models are linked by an analytic expression which relates the localization length to the percolation threshold and critical exponent. The relation is confirmed both numerically and experimentally through measurements of the relative conductivity of Tris(4-carbazoyl-9-ylphenyl)amine (TCTA) :1,3-bis(3,5-dipyrid-3-yl-phenyl)benzene (BmPyPb) mixtures with different concentrations, where the TCTA plays a role as hole conductor and the BmPyPb as hole insulator. The analytic relation may allow the rational design of mixed layers of small molecules for high-performance OLEDs.
ISSN:2158-3226
2158-3226
DOI:10.1063/1.4948591