Elucidating the Spatial Arrangement of Emitter Molecules in Organic Light-Emitting Diode Films.
The effect of varying the emitter concentration on the structural properties of an archetypal phosphorescent blend consisting of 4,4'-bis(N-carbazolyl)biphenyl and tris(2-phenylpyridyl)iridium(III) has been investigated using non-equilibrium molecular dynamics (MD) simulations that mimic the process of vacuum deposition. By comparison with reflectometry measurements, we show that the simulations provide an accurate model of the average density of such films. The emitter molecules were found not to be evenly distributed throughout film, but rather they can form networks that provide charge and/or energy migration pathways, even at emitter concentrations as low as ≈5 weight percent. At slightly higher concentrations, percolated networks form that span the entire system. While such networks would give improved charge transport, they could also lead to more non-radiative pathways for the emissive state and a resultant loss of efficiency.
Centre for Organic Photonics & Electronics, School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia Campus, Brisbane, 4072, Australia.
Claire
C
Tonnelé
Molecular Dynamics Group, School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia Campus, Brisbane, 4072, Australia.
Martin
0000-0002-9570-2376
M
Stroet
Molecular Dynamics Group, School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia Campus, Brisbane, 4072, Australia.
Bertrand
0000-0003-2305-1452
B
Caron
Centre for Organic Photonics & Electronics, School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia Campus, Brisbane, 4072, Australia.
Andrew J
AJ
Clulow
Centre for Organic Photonics & Electronics, School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia Campus, Brisbane, 4072, Australia.
Ravi C R
RCR
Nagiri
Molecular Dynamics Group, School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia Campus, Brisbane, 4072, Australia.
Alpeshkumar K
0000-0002-8181-1619
AK
Malde
Centre for Organic Photonics & Electronics, School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia Campus, Brisbane, 4072, Australia.
Paul L
0000-0003-3405-3517
PL
Burn
Centre for Organic Photonics & Electronics, School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia Campus, Brisbane, 4072, Australia.
Ian R
IR
Gentle
Molecular Dynamics Group, School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia Campus, Brisbane, 4072, Australia.
Alan E
0000-0001-5880-4798
AE
Mark
Centre for Organic Photonics & Electronics, School of Mathematics and Physics, The University of Queensland, St Lucia Campus, Brisbane, 4072, Australia.
Benjamin J
BJ
Powell
Ir(ppy)3:CBP blends; OLEDs; connectivity; evaporation; morphology