Efficiency Enhancement of Organic Light‐Emitting Diodes Incorporating a Highly Oriented Thermally Activated Delayed Fluorescence Emitter | Zendy

Mayr Christian | Zendy; Lee Sae Youn | Zendy; Schmidt Tobias D. | Zendy; Yasuda Takuma | Zendy; Adachi Chihaya | Zendy; Brütting Wolfgang | Zendy

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Efficiency Enhancement of Organic Light‐Emitting Diodes Incorporating a Highly Oriented Thermally Activated Delayed Fluorescence Emitter

Author(s) -

Mayr Christian,

Lee Sae Youn,

Schmidt Tobias D.,

Yasuda Takuma,

Adachi Chihaya,

Brütting Wolfgang

Publication year - 2014

Publication title -

advanced functional materials

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 6.069

H-Index - 322

eISSN - 1616-3028

pISSN - 1616-301X

DOI - 10.1002/adfm.201400495

Subject(s) - common emitter , oled , materials science , quantum efficiency , optoelectronics , photoluminescence , radiative transfer , exciton , fluorescence , quantum yield , diode , optics , layer (electronics) , nanotechnology , physics , condensed matter physics

An organic light‐emitting diode (OLED) with the blue emitter CC2TA showing thermally activated delayed fluorescence (TADF) is presented exhibiting an external quantum efficiency ( η EQE) of 11% ± 1%, which clearly exceeds the classical limit for fluorescent OLEDs. The analysis of the emission layer by angular dependent photoluminescence (PL) measurements shows a very high degree of 92% horizontally oriented transition dipole moments. Excited states lifetime measurements of the prompt fluorescent component under PL excitation yield a radiative quantum efficiency of 55% of the emitting species. Thus, the radiative exciton fraction has to be significantly higher than 25% due to TADF. Performing a simulation based efficiency analysis for the OLED under investigation allows for a quantification of individual contributions to the efficiency increase originating from horizontal emitter orientation and TADF. Remarkably, the strong horizontal emitter orientation leads to a light‐outcoupling efficiency of more than 30%.

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