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Phys. Rev. B 60, 14422–14428 (1999)

Excitonic singlet-triplet ratio in a semiconducting organic thin film

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M. A. Baldo and D. F. O’Brien*
Center for Photonics and Optoelectronic Materials (POEM), Department of Electrical Engineering and the Princeton Materials Institute, Princeton University, Princeton, New Jersey 08544

M. E. Thompson
Department of Chemistry, University of Southern California, Los Angeles, California 90089

S. R. Forrest
Center for Photonics and Optoelectronic Materials (POEM), Department of Electrical Engineering and the Princeton Materials Institute, Princeton University, Princeton, New Jersey 08544

Received 1 June 1999; published in the issue dated 15 November 1999

A technique is presented to determine the spin statistics of excitons formed by electrical injection in a semiconducting organic thin film. With the aid of selective addition of luminescent dyes, we generate either fluorescence or phosphorescence from the archetype organic host material aluminum tris (8-hydroxyquinoline) (Alq3). Spin statistics are calculated from the ratio of fluorescence to phosphorescence in the films under electrical excitation. After accounting for varying photoluminescent efficiencies, we find a singlet fraction of excitons in Alq3 of (22±3)%.

© 1999 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevB.60.14422
DOI:
10.1103/PhysRevB.60.14422
PACS:
71.35.Cc, 72.80.Le

*Present address: Department of Physics, Trinity College Dublin, Dublin 2, Ireland.

 
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