Design Rules for Charge-Transport Efficient Host Materials for Phosphorescent Organic Light-Emitting Diodes
- 10 August 2012
- journal article
- research article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 134 (33), 13818-13822
- https://doi.org/10.1021/ja305310r
Abstract
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 pi-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.Keywords
This publication has 38 references indexed in Scilit:
- Microscopic Simulations of Charge Transport in Disordered Organic SemiconductorsJournal of Chemical Theory and Computation, 2011
- Relationship between supramolecular assembly and charge-carrier mobility in perylenediimide derivatives: The impact of side chainsJournal of Materials Chemistry, 2011
- High‐Efficiency Blue and White Organic Light‐Emitting Devices Incorporating a Blue Iridium Carbene ComplexAdvanced Materials, 2010
- Density-functional based determination of intermolecular charge transfer properties for large-scale morphologiesPhysical Chemistry Chemical Physics, 2010
- n-Type Charge Transport and Mobility of Fluorinated Perylene Bisimide SemiconductorsThe Journal of Physical Chemistry B, 2010
- Current Status of the AMOEBA Polarizable Force FieldThe Journal of Physical Chemistry B, 2010
- Charge Mobility of Discotic Mesophases: A Multiscale Quantum and Classical StudyPhysical Review Letters, 2007
- 11.2: Efficient Deep Blue Triplet Emitters for OLEDsSID Symposium Digest of Technical Papers, 2006
- Application of admittance spectroscopy to evaluate carrier mobility in organic charge transport materialsJournal of Applied Physics, 2006
- Endothermic energy transfer: A mechanism for generating very efficient high-energy phosphorescent emission in organic materialsApplied Physics Letters, 2001