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Title: Effects of Charge Balance and Exciton Confinement on the Operational Lifetime of Blue Phosphorescent Organic Light-Emitting Diodes

Authors:
;
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1352967
Grant/Contract Number:
EE000707
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Physical Review Applied
Additional Journal Information:
Journal Volume: 7; Journal Issue: 4; Related Information: CHORUS Timestamp: 2017-04-24 22:08:52; Journal ID: ISSN 2331-7019
Publisher:
American Physical Society
Country of Publication:
United States
Language:
English

Citation Formats

Coburn, Caleb, and Forrest, Stephen R. Effects of Charge Balance and Exciton Confinement on the Operational Lifetime of Blue Phosphorescent Organic Light-Emitting Diodes. United States: N. p., 2017. Web. doi:10.1103/PhysRevApplied.7.041002.
Coburn, Caleb, & Forrest, Stephen R. Effects of Charge Balance and Exciton Confinement on the Operational Lifetime of Blue Phosphorescent Organic Light-Emitting Diodes. United States. doi:10.1103/PhysRevApplied.7.041002.
Coburn, Caleb, and Forrest, Stephen R. Mon . "Effects of Charge Balance and Exciton Confinement on the Operational Lifetime of Blue Phosphorescent Organic Light-Emitting Diodes". United States. doi:10.1103/PhysRevApplied.7.041002.
@article{osti_1352967,
title = {Effects of Charge Balance and Exciton Confinement on the Operational Lifetime of Blue Phosphorescent Organic Light-Emitting Diodes},
author = {Coburn, Caleb and Forrest, Stephen R.},
abstractNote = {},
doi = {10.1103/PhysRevApplied.7.041002},
journal = {Physical Review Applied},
number = 4,
volume = 7,
place = {United States},
year = {Mon Apr 24 00:00:00 EDT 2017},
month = {Mon Apr 24 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1103/PhysRevApplied.7.041002

Citation Metrics:
Cited by: 4works
Citation information provided by
Web of Science

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  • We compared the performance of phosphorescent white organic light emitting diodes (WOLEDs) with red-blue-green and green-blue-red sequent emissive layers. It was found that the influence of red and green dopants on electron and hole transport in emissive layers leads to the large difference in the efficiency of fabricated WOLEDs. This improvement mechanism is well investigated by the current density-voltage characteristics of single-carrier devices based on dopant doped emissive layers and the comparison of electroluminescent and photoluminescence spectra, and attributed to the different change of charge carrier transport by the dopants. The optimized device achieves a maximum power efficiency, current efficiency,more » and external quantum efficiency of 37.0 lm/W, 38.7 cd/A, and 17.7%, respectively, which are only reduced to 32.8 lm/W, 38.5 cd/A, and 17.3% at 1000 cd/m{sup 2} luminance. The critical current density is as high as 210 mA/cm{sup 2}. It can be seen that the efficiency roll-off in phosphorescent WOLEDs can be well improved by effectively designing the structure of emissive layers.« less
  • Single-layer blue phosphorescence organic light emitting diodes (OLEDs) with either small-molecule or polymer hosts are fabricated using solution process and the performances of devices with different hosts are investigated. The small-molecule device exhibits luminous efficiency of 14.7 cd/A and maximum power efficiency of 8.39 lm/W, which is the highest among blue phosphorescence OLEDs with single-layer solution process and small molecular hosts. Using the same solution process for all devices, comparison of light out-coupling enhancement, with brightness enhancement film (BEF), between small-molecule and polymer based OLEDs is realized. Due to different dipole orientation and anisotropic refractive index, polymer-based OLEDs would trap less lightmore » than small molecule-based OLEDs internally, about 37% better based simulation results. In spite of better electrical and spectroscopic characteristics, including ambipolar characteristics, higher carrier mobility, higher photoluminescence quantum yield, and larger triplet state energy, the overall light out-coupling efficiency of small molecule-based devices is worse than that of polymer-based devices without BEF. However, with BEF for light out-coupling enhancement, the improved ratio in luminous flux and luminous efficiency for small molecule based device is 1.64 and 1.57, respectively, which are significantly better than those of PVK (poly-9-vinylcarbazole) devices. In addition to the theoretical optical simulation, the experimental data also confirm the origins of differential light-outcoupling enhancement. The maximum luminous efficiency and power efficiency are enhanced from 14.7 cd/A and 8.39 lm/W to 23 cd/A and 13.2 lm/W, respectively, with laminated BEF, which are both the highest so far for single-layer solution-process blue phosphorescence OLEDs with small molecule hosts.« less
  • Due to the poor operational lifetime of blue phosphorescent dopants and blue thermally activated delayed fluorescent (TADF) materials, hybrid white organic light-emitting diodes (WOLEDs) with conventional blue fluorescent emitters are still preferred for commercial applications in general lighting. However, the improvement in the overall efficiency of hybrid WOLEDs has been limited due to energy losses during the energy transfer process and exciton quenching after the spatial separation of the singlet and triplet excitons. Here we demonstrate the development of a Spatial Exciton Allocation Strategy (SEAS) to achieve close to 100% internal quantum efficiency (IQE) in blue-yellow complementary color hybrid WOLEDs.more » The employed blue fluorophore not only has a resonant triplet level with the yellow phosphor to reduce energy loss during energy transfer processes and triplet–triplet annihilation (TTA), but also has a resonant singlet level with the electron transport layer to extend singlet exciton distribution and enhance both singlet and triplet exciton utilization. Thus, the resulting hybrid WOLEDs exhibited 104 lm W -1 efficacy at 100 cd m -2 and 74 lm W -1 at 1000 cd m -2 with CIE coordinates of (0.42, 0.44) which is warm white and suitable for indoor lighting.« less
  • We have demonstrated high-efficiency greenish-blue phosphorescent organic light-emitting diodes (PHOLEDs) based on a dimesitylboryl-functionalized C^N chelate Pt(II) phosphor, Pt(m-Bptrz)(t-Bu-pytrz-Me). Using a high triplet energy platform and optimized double emissive zone device architecture results in greenish-blue PHOLEDs that exhibit an external quantum efficiency of 24.0% and a power efficiency of 55.8 lm/W. This record high performance is comparable with that of the state-of-the-art Ir-based sky-blue organic light-emitting diodes.