Work

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

Year: 2014

Type: article

Abstract: An organic light‐emitting diode (OLED) with the blue emitter CC2TA showing thermally activated delayed fluorescence (TADF) is presented exhibiting an external quantum efficiency ( ) 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%.

Source: Advanced Functional Materials

DOI: 10.1002/adfm.201400495

Authors: Christian Mayr, Sae Youn Lee, Tobias D. Schmidt, Takuma Yasuda, Chihaya Adachi, Wolfgang Brütting

Institutions: University of Augsburg, Kyushu University

Language: English

Topic: Organic Light-Emitting Diodes Research

Subfield: Electrical and Electronic Engineering

Field: Engineering

Domain: Physical Sciences

Open Access status: green

Funders: Deutsche Forschungsgemeinschaft, Bayerische Forschungsstiftung, Japan Society for the Promotion of Science

Awards: Development of novel organic light-emitting diodes displaying circularly polarized luminescence, G6858461175, G8165728025