Measuring the dipole orientation in OLEDs

Michael Flämmich; Stephan Roth; Norbert Danz; Dirk Michaelis; Andreas H. Bräuer; Malte C. Gather; Klaus Meerholz

doi:10.1117/12.853866

18 May 2010 Measuring the dipole orientation in OLEDs

Michael Flämmich, Stephan Roth, Norbert Danz, Dirk Michaelis, Andreas H. Bräuer, Malte C. Gather, Klaus Meerholz

Proceedings Volume 7722, Organic Photonics IV; 77220D (2010) https://doi.org/10.1117/12.853866
Event: SPIE Photonics Europe, 2010, Brussels, Belgium

Abstract

The orientation of the emissive dipole moments in organic light-emitting diodes (OLEDs) has a major impact on the optical outcoupling efficiency and, consequently, on the device performance as well as on possible optimization strategies. In this contribution we discuss a general method to quantify the amounts of parallel and perpendicular emissive sites in OLEDs. The presented in-situ-method is based on measurements of the far-field emission of an electrically operating device and corresponding optical reverse simulations. For the reverse simulation we take advantage of the fact that perpendicular dipoles only contribute to transverse-magnetic polarized light emission. In general, the method can be applied to all classes of emissive materials for OLEDs, including small-molecule and dendrimer materials. In the present study we utilize bottom emitting polymeric OLEDs with two different stack architectures: (A) a conventional OLED stack optimized for maximum performance and (B) a well adapted OLED stack, where the contribution of perpendicularly oriented dipoles to the radiation pattern in air is optically enhanced. We demonstrate that for OLED (A) perpendicular dipoles are "invisible" in the optical far-field, because almost all light from perpendicularly oriented dipoles is trapped inside the OLED stack. Consequently, no information about the emitter orientation can be gained from the radiation pattern of this device. In contrast, OLED (B) clearly shows that the radiation pattern is generated by 93.5 % parallel and 6.5 % perpendicular dipoles. Assuming a Gaussian distribution of dipole orientations in the particular emissive material, the dipoles stagger around the preferred parallel direction with an 1/e-angle of ± 22°.

Citation Download Citation

Michael Flämmich, Stephan Roth, Norbert Danz, Dirk Michaelis, Andreas H. Bräuer, Malte C. Gather, and Klaus Meerholz "Measuring the dipole orientation in OLEDs", Proc. SPIE 7722, Organic Photonics IV, 77220D (18 May 2010); https://doi.org/10.1117/12.853866

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available