The authors report on an internal device modification for multilayer organic light-emitting diodes (OLEDs) with enhanced efficiency that promises high compatibility with conventional manufacturing processes. By copolymerization of a hole-conducting monomer with a compound possessing a lower refractive index, a hole-transport layer with reduced optical density but slightly reduced hole-transport properties is formed. Multilayer OLEDs based on this reduced-index layer show a 25% increased efficiency compared to reference devices. The results are compared to optical simulations of the dipole emission from thin organic films. It is found that the efficiency improvement is only to some extent due to enhanced outcoupling resulting directly from the reduced refractive index but primarily due to a change of the width of the emission zone.
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10 September 2007
Research Article|
September 10 2007
Enhanced efficiency of multilayer organic light-emitting diodes with a low-refractive index hole-transport layer: An effect of improved outcoupling?
Anne Köhnen;
Anne Köhnen
Institut für Physikalische Chemie,
Universität zu Köln
, Luxemburgerstr. 116, Köln 50939, Germany
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Malte C. Gather;
Malte C. Gather
Institut für Physikalische Chemie,
Universität zu Köln
, Luxemburgerstr. 116, Köln 50939, Germany
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Nina Riegel;
Nina Riegel
Institut für Physikalische Chemie,
Universität zu Köln
, Luxemburgerstr. 116, Köln 50939, Germany
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Philipp Zacharias;
Philipp Zacharias
Institut für Physikalische Chemie,
Universität zu Köln
, Luxemburgerstr. 116, Köln 50939, Germany
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Klaus Meerholz
Institut für Physikalische Chemie,
Universität zu Köln
, Luxemburgerstr. 116, Köln 50939, Germany
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a)
Electronic mail: [email protected]
Appl. Phys. Lett. 91, 113501 (2007)
Article history
Received:
March 09 2007
Accepted:
July 28 2007
Citation
Anne Köhnen, Malte C. Gather, Nina Riegel, Philipp Zacharias, Klaus Meerholz; Enhanced efficiency of multilayer organic light-emitting diodes with a low-refractive index hole-transport layer: An effect of improved outcoupling?. Appl. Phys. Lett. 10 September 2007; 91 (11): 113501. https://doi.org/10.1063/1.2773930
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