Excitonic singlet-triplet ratio in a semiconducting organic thin film

M. A. Baldo; D. F. O’Brien; M. E. Thompson; S. R. Forrest

doi:10.1103/PhysRevB.60.14422

Excitonic singlet-triplet ratio in a semiconducting organic thin film

M. A. Baldo, D. F. O’Brien, M. E. Thompson, and S. R. Forrest

Phys. Rev. B 60, 14422 – Published 15 November 1999

Abstract

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) $({Alq}_{3}) .$ 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 ${Alq}_{3}$ of $(22 \pm 3) % .$

Received 1 June 1999

DOI:https://doi.org/10.1103/PhysRevB.60.14422

Authors & Affiliations

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

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

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Vol. 60, Iss. 20 — 15 November 1999

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Physical Review B

covering condensed matter and materials physics