The authors present Raman scattering studies from ethyl-hexyl substituted polyfluorene (PF)-based light-emitting diodes in the presence of injected and photogenerated charge carriers. The Raman background systematically increases with increased charge density and the Raman peaks exhibit asymmetric line shapes characteristic of a Breit-Wigner-Fano (BWF) resonance, indicating interference effects between the electronic continuum and phonons. A complete BWF line shape analysis of the intraring stretch mode at 1605cm1 is provided. These results are compared with p-doped PF; by increasing the doping concentration, it is seen that the center of the electronic continuum lies at 0.2eV.

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