Biexcitons in π-conjugated oligomers: Intensity-dependent femtosecond transient-absorption study

Victor I Klimov, D. W. McBranch, N. Barashkov, J. Ferraris

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We report femtosecond transient-absorption (TA) studies of a five-ring oligomer of poly(para-phenylene vinylene) prepared in two different forms: solid-state films and dilute solutions. At high pump fluences, in both types of samples, we observe generation of two-exciton states, which are detected by the evolution of TA spectra and dynamics with increasing pump intensity. In solutions, double excitation of molecules results in the formation of stable biexcitons with enhanced oscillator strength, leading to an increased efficiency of the radiative decay and a superlinear pump dependence of the stimulated emission. In solid-state samples, the two-exciton states are unstable and decay on the subpicosecond time scale due to ultrafast charge transfer, accompanied by generation of interchain excitons.

Original languageEnglish
Pages (from-to)7654-7662
Number of pages9
JournalPhysical Review B - Condensed Matter and Materials Physics
Issue number12
Publication statusPublished - Sep 15 1998


ASJC Scopus subject areas

  • Condensed Matter Physics

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