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n-Type host materials based on nitrile and triazine substituted tricyclic aromatic compounds for high-performance blue thermally activated delayed fluorescence devices

Title
n-Type host materials based on nitrile and triazine substituted tricyclic aromatic compounds for high-performance blue thermally activated delayed fluorescence devices
Authors
Jang, SeokhoonLee, Kyung HyungHong, SoojinLee, Jun YeobLee, Youngu
DGIST Authors
Lee, Youngu
Issue Date
2021-03
Citation
Dyes and Pigments, 187, 109091
Type
Article
Article Type
Article
Author Keywords
OLEDTADFn-Type hostTriplet energyNitrile
Keywords
Thermally activated delayed fluorescencesOrganic light emitting diodes (OLED)CyanidesEfficiencyElectronsEnergyFluorescenceTemperatureTypeCyanidesElectron transport propertiesFluorescenceMolecular orbitalsOrganic pollutantsSound insulating materialsTemperatureThermodynamic stabilityThiopheneTransport propertiesUltraviolet photoelectron spectroscopyEfficient electron injectionExternal quantum efficiencyHigh thermal stabilityLow temperature photoluminescenceLowest unoccupied molecular orbitalMolecular building blocksOrganic light-emitting devices
ISSN
0143-7208
Abstract
Novel n-type host materials based on tricyclic aromatic compounds, dibenzo[b,d]furan and dibenzo[b,d]thiophene (2Trz6CNDBF and 2Trz6CNDBT), have been successfully synthesized and characterized for high-performance blue thermally activated delayed fluorescence (TADF) organic light-emitting devices (OLEDs). Dibenzo[b,d]furan and dibenzo[b,d]thiophene were utilized as central molecular building blocks to achieve excellent thermal stability and high triplet energy (ET). Nitrile and diphenyltriazine functional groups were introduced at the 6- and 2- positions of the central building blocks to achieve low-lying lowest unoccupied molecular orbital (LUMO) energy levels, high ET, and excellent electron transport properties. UV–Vis absorption, low-temperature photoluminescence, and ultraviolet photoelectron spectroscopy analysis showed that 2Trz6CNDBF and 2Trz6CNDBT possessed high ET (2.95 and 2.88 eV) and low-lying LUMO energy levels (−3.43 and −3.16 eV) that were well-matched with a blue TADF emitter, 5CzCN. Moreover, the electron-only device (EOD) result revealed that 2Trz6CNDBF and 2Trz6CNDBT had excellent electron transport properties. Blue TADF OLEDs fabricated with a p-type host material, mCBP, and n-type host, 2Trz6CNDBF or 2Trz6CNDBT, exhibited lower driving voltages (3.34 and 3.26 V, respectively) than a TADF OLED with only a p-type host material, mCBP (3.83 V). Blue TADF OLEDs with 2Trz6CNDBF and 2Trz6CNDBT exhibited superior external quantum efficiency (ηext, 15.6 and 14.7%), current efficiency (ηce, 33.8 and 32.7 cd A−1), and power efficiency (ηpe, 25.6 and 25.7 lm W−1), respectively. The ηext and ηce of blue TADF OLEDs with 2Trz6CNDBF and 2Trz6CNDBT increased by more than 70% and ηpe by approximately 150% compared to those of the TADF OLED with a single p-type host, mCBP. In addition, the device lifetimes of blue TADF OLEDs with 2Trz6CNDBF and 2Trz6CNDBT increased by more than 1000%. The efficient electron injection by the low-lying LUMO energy level, effective exciton confinement by high ET, and high thermal stability of the film morphology provided the enhanced efficiency and lifetime for blue TADF OLEDs with 2Trz6CNDBF and 2Trz6CNDBT. © 2020 Elsevier Ltd
URI
http://hdl.handle.net/20.500.11750/12605
DOI
10.1016/j.dyepig.2020.109091
Publisher
Elsevier BV
Related Researcher
  • Author Lee, Youngu Organic & Printed Electronics Laboratory(OPEL)
  • Research Interests OTF Solar cell; OLED; Printed Electronics; 유기박막형 태양전지
Files:
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Collection:
Department of Energy Science and EngineeringOrganic & Printed Electronics Laboratory(OPEL)1. Journal Articles


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