High-efficiency fluorescent organic light-emitting diodes enabled by triplet-triplet annihilation and horizontal emitter orientation

A green organic light-emitting diode with the fluorescent emitter Coumarin 545T shows an external quantum efficiency (ηEQE) of 6.9%, clearly exceeding the classical limit of 5% for fluorescent emitters. The analysis of the angular dependent photoluminescence spectrum of the emission layer reveals th...

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Bibliographic Details
Published in:	Applied physics letters Vol. 105; no. 18; p. 183304
Main Authors:	Mayr, Christian, Schmidt, Tobias D., Brütting, Wolfgang
Format:	Journal Article
Language:	English
Published:	Melville American Institute of Physics 03-11-2014
Subjects:	ANNIHILATION Applied physics CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS Coumarin Diodes DIPOLE MOMENTS Efficiency ELECTROLUMINESCENCE Emission analysis Emitters FLUORESCENCE Horizontal orientation LIGHT EMITTING DIODES MATERIALS SCIENCE Organic light emitting diodes PHOTOLUMINESCENCE QUANTUM EFFICIENCY SIMULATION TRIPLETS
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Summary:	A green organic light-emitting diode with the fluorescent emitter Coumarin 545T shows an external quantum efficiency (ηEQE) of 6.9%, clearly exceeding the classical limit of 5% for fluorescent emitters. The analysis of the angular dependent photoluminescence spectrum of the emission layer reveals that 86% of the transition dipole moments are horizontally oriented. Furthermore, transient electroluminescence measurements demonstrate the presence of a delayed emission originating from triplet-triplet annihilation. A simulation based efficiency analysis reveals quantitatively the origin for the high ηEQE: a radiative exciton fraction higher than 25% and a light-outcoupling efficiency of nearly 30%.
ISSN:	0003-6951 1077-3118
DOI:	10.1063/1.4901341