Abstract

Optically and electrically detected magnetic resonance studies of luminescent π-conjugated thin films and organic light-emitting devices (OLEDs) have provided striking insight into their various excitations. The salient feature in the photoluminescence (PL)-detected magnetic resonance (PLDMR) of luminescent π-conjugated polymers and small molecules is the positive (PL-enhancing) spin 1/2 polaron resonance. Although its nature is still debated, there is very strong evidence that it results from reduced quenching of the luminescent singlet excitons (SEs) by reduced populations of polarons and triplet excitons (TEs). The reduction in these populations is due, in turn, to the well-known strongly spin-dependent quenching of TEs by polarons. This is also plausible due to the simple observation that, under typical steady-state conditions, the populations of these species overwhelms the SE population (by > 100 fold under photoexcitation, by > 104 fold under carrier injection). The positive (PL-enhancing) spin 1 TE resonances are similarly due to reduced quenching of SEs by TEs. These scenarios lead to the conclusion that the internal quantum efficiency of fluorescent (as opposed to phosphorescent) OLEDs is limited to 25%. The negative (PL-, electroluminescence (EL)- and electrical current (E)-quenching) resonances observed under short wavelength photoexcitation or carrier injection are due to enhanced formation of bipolarons or trions at specific sites, and their significance is also discussed.

© 2010 Optical Society of America

PDF Article
More Like This
Current Issues in the Science and Technology of Organic Light-Emitting Devices (OLEDs)

Joseph Shinar
FA2 Optical Interference Coatings (OIC) 2004

Charge Carriers And Triplets In OLED Devices Studied By Electrically Detected Magnetic Resonance

Thomas Pawlik, Denis Kondakov, Ralph Young, and Marina Kondakova
OPTuA4 Organic Photonics and Electronics (OPE) 2006

Understanding Improved Lifetime in Mixed Emissive Layer Organic Light-Emitting Devices (OLEDs)

John S. Bangsund and Russell J. Holmes
STu1C.5 Solid-State Lighting (SSL) 2017

References

You do not have subscription access to this journal. Citation lists with outbound citation links are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access OSA Member Subscription