Enhancing the efficiency of organic LEDs through spin-orbit coupling of charge-transfer states
Name
71844614-MIT.pdf
Description
Full printable version
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2.15 MB
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Checksum (MD5)
60a8a2889070b6e10019db4c217b2358
Author(s)
Rivoire, Kelley (Kelley E.)
Advisor(s)
Marc A. Baldo.
Date Issued
2006
Publisher
Massachusetts Institute of Technology
Abstract
In this thesis, the possibility of enhancing the efficiency of small molecule organic light-emitting diodes through spin-orbit effects is examined. Because only singlet spin states, statistically one quarter of the total possible states, emit fluorescent light, it has generally been thought that a maximum of 25% efficiency could be attained without the addition of an emissive phosphor. Here, we present evidence that this is not a fundamental limit. Two OLED structures have been studied, each providing evidence that the efficiency of the OLED can be enhanced by the use of a heavy-metal material to mix spin in charge-transfer states. A structure with a heavy-metal mixing layer placed beside a neat emissive layer was found to show a (2.5 ± 0.3) times enhancement in the efficiency compared with an OLED without the heavy-metal layer. However, differences in the electroluminescent emission spectra made attributing this result to spin statistics alone difficult. In a structure with the the heavy-metal mixing layer placed next to a fluorescent dye doped into a host, a (2.7 ± 0.2) times enhancement in the efficiency is measured.
Description
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2006.
Includes bibliographical references (p. 59-63).
Subjects
Physics.
MIT Department
Massachusetts Institute of Technology. Department of Physics
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