Biexcitons in {pi}-conjugated oligomers: Intensity-dependent femtosecond transient-absorption study
- Chemical Science and Technology Division, CST-6, Mail Stop J585, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
- Chemistry Department, University of Texas, Dallas, Texas 75083 (United States)
We report femtosecond transient-absorption (TA) studies of a five-ring oligomer of poly({ital 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. {copyright} {ital 1998} {ital The American Physical Society}
- OSTI ID:
- 658496
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 58, Issue 12; Other Information: PBD: Sep 1998
- Country of Publication:
- United States
- Language:
- English
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