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Conjugated Polymer Fluorescence: Interplay Of Correlations And Alternation

Published online by Cambridge University Press:  16 February 2011

Z. G. Soos ,
D. S. Galvão ,
S. Etemad  and
R. G. Keplero
Z. G. Soos
Affiliation:
Department of Chemistry, Princeton University, Princeton, NJ 08544
D. S. Galvão
Affiliation:
Bell Communications Research, Red Bank, NJ 07701 Universidade Estadual de Campinas, Departamento de Fisica Aplicada, 13081, Campinas, SP, Brazil
S. Etemad
Affiliation:
Bell Communications Research, Red Bank, NJ 07701
R. G. Keplero
Affiliation:
Sandia National Laboratories, Albuquerque, NM 87185
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Extract

Conjugated polymers have been intensively studied in connection with high conductivity on doping, large nonlinear optical responses in their semiconducting state, and recently[1] as novel light-emitting diodes (LEDs). Many different polymers are realized in Fig. 1 on varying the substituents R, including the best characterized examples[2,3] that have centrosymmetric conjugated backbones in their idealized extended geometry. The PS and PPV families fluoresce strongly, the PT family Moderately, and the PDA's or PA hardly at all. We have related [4,5] polymer fluorescence to the nature of the lowest singlet excited state, Si, which in C2h symmetry is either a dipole-allowed Bu or a two-photon allowed Ag state. Since the ground state is Ag, S1 is either 1B or 2A and fluorescence requires E (1B) < E(2A). The idea is simply that radiationless decay wins out for the low excitation energies and many vibrational degrees of freedom of conjugated polymers unless Si has a strong transition dipole to the ground state.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 328: Symposium Q – Electrical, Optical, and Magnetic Properties of Organic Solid State Materials , 1993 , 383
Copyright
Copyright © Materials Research Society 1994

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References

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