High performance blue-emitting organic light-emitting diodes from thermally activated delayed fluorescence: A guest/host ratio study

Journal Article · Tue Aug 07 00:00:00 EDT 2018 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.5041447· OSTI ID:1540237

Zhang, Xiaoqing ^[1]; Fuentes-Hernandez, Canek ^[1]; Zhang, Yadong ^[1]; Cooper, Matthew W. ^[1]; Barlow, Stephen ^[1]; Marder, Seth R. ^[1]; Kippelen, Bernard  ^[1]

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1. Georgia Inst. of Technology, Atlanta, GA (United States)

Emitters displaying thermally activated delayed fluorescence (TADF) can lead to highly efficient organic light-emitting diodes (OLEDs). Such emitters are usually incorporated into the emissive layer (EML) at a relatively low concentration (< 20 wt. %) with respect to a host material, a guest-host approach inherited from conventional fluorescent or phosphorescent OLEDs. Here, detailed studies on OLEDs, in which the concentration of oBFCzTrz (a blue-emitter displaying TADF) in a DPEPO host was varied from 8 to 100 wt. %, reveals that oBFCzTrz displays ambipolar transport and limited fluorescence-quenching due to aggregation. For instance, a neat film of oBFCzTrz maintains a photoluminescence quantum yield of 82%. We demonstrate that OLEDs with an EML having an oBFCzTrz concentration of 50 wt. % in DPEPO yield a maximum external quantum efficiency (EQE) of 25.5% with an EQE roll-off of 10% in the range from 10 to 1,000 cd/m2 and Commission Internationale de l’Eclairage color coordinates of (0.20, 0.44). OLEDs with smaller or larger oBFCzTrz concentrations display smaller maximum EQE values. OLEDs with a neat oBFCzTrz EML display a maximum EQE of 14.0%. Time-resolved electroluminescent decay studies, and analysis using a simple model, reveal significant differences in transport, trapping, and recombination in these devices.

• Research Organization: Georgia Institute of Technology, Atlanta, GA (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE)
• Grant/Contract Number: EE0008205
• OSTI ID: 1540237
• Alternate ID(s): OSTI ID: 1463225; OSTI ID: 1767166
• Journal Information: Journal of Applied Physics, Vol. 124, Issue 5; ISSN 0021-8979
• Publisher: American Institute of Physics (AIP)
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
36 MATERIALS SCIENCE
Excitons
Photoluminescence
Quantum efficiency
Fluorescence quenching
Light emitting diodes
Electric currents
Charge transport
Polarons
Solid state lighting
Organic light-emitting diodes