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Exciton annihilation in a polyfluorene : low threshold for singlet-singlet annihilation and the absence of singlet-triplet annihilation.

King, S.M. and Dai, D. and Rothe, C. and Monkman, A.P. (2007) 'Exciton annihilation in a polyfluorene : low threshold for singlet-singlet annihilation and the absence of singlet-triplet annihilation.', Physical review B., 76 (8). 085204.

Abstract

Ultrafast photoinduced absorption measurements have been used to directly investigate singlet-singlet annihilation in polyfluorene. The pump fluence threshold for annihilation to dominate the decay was measured to be ∼1 μJ cm−2 corresponding to an excitation density of 1.5×1017 cm−3. The annihilation rate was found to be faster than that expected from a simple dipole-dipole interaction. This is ascribed to the additional influence of diffusion which, because of the dispersive nature of the exciton migration, has strong time dependence as the singlet excitons thermalize in the density of states as well as the expected intrinsic time dependence from a diffusion controlled process. Also, a comparable background level of triplets was created in the film to study the effect of singlet-triplet annihilation, which surprisingly, given the low threshold for singlet-singlet annihilation, was found to be negligible.

Item Type:Article
Full text:PDF - Published Version (240Kb)
Status:Peer-reviewed
Publisher Web site:http://dx.doi.org/10.1103/PhysRevB.76.085204
Publisher statement:© 2007 by The American Physical Society. All rights reserved.
Record Created:18 Oct 2010 12:35
Last Modified:19 Oct 2010 10:45

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