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

Journal Article · 06 August 2018 · Journal of Applied Physics

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

Zhang, Xiaoqing ^[1]; Fuentes-Hernandez, Canek ^[2]; Zhang, Yadong ^[2]; Cooper, Matthew W. ^[2]; Barlow, Stephen ^[2]; Marder, Seth R. ^[2]; Kippelen, Bernard  ^[2]

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1. Georgia Inst. of Technology, Atlanta, GA (United States); DOE/OSTI
2. Georgia Inst. of Technology, Atlanta, GA (United States)

Emitters displaying thermally activated delayed fluorescence (TADF) can drive 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 method inherited from conventional fluorescent or phosphorescent OLEDs. In this work, 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 determine 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 1000 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%. Finally, 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 Inst. 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: 1767166; OSTI ID: 1463225
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 5 Vol. 124; ISSN 0021-8979
• Publisher: American Institute of Physics (AIP)Copyright Statement
• Country of Publication: United States
• Language: English