Title Ultrafast dynamics of singlet-singlet and singlet-triplet exciton annihilation in poly(3-2 '-methoxy-5 '-octylphenyl)thiophene films
Author/s Yuri Zaushitsyn, Kim Jespersen, Leonas Valkunas, Villy Sundström, Arkady Yartsev
Department/s Chemical Physics (S)
Full-text Full text is not available in this archive
Alternative location (URL) http://dx.doi.org/10.1103/Phys... Restricted Access (Alternative Location)
Publication/Series Physical Review B
Publishing year 2007
Volume 75
Issue 19
Document type Journal article
Status published
Quality controlled yes
Language English
Publisher American Physical Society
Abstract English Singlet-singlet (S-S) and singlet-triplet (S-T) exciton annihilation was studied in poly(3-2(')-methoxy-5(')octylphenyl)thiophene films. For the S-S exciton annihilation studies, transient absorption spectroscopy at excitation laser pulse fluences of 1.2x10(13)-4.4x10(14) photons/cm(2) and 2.5 kHz pulse repetition rate was applied. The obtained kinetics demonstrate a typical nonexponential character with intensity-dependent amplitudes and lifetimes. In time-resolved fluorescence experiments, low excitation pulse fluences of 1.6x10(9)-2.2x10(12) photons/cm(2) at high repetition rates of 0.4, 0.8, 4, and 81 MHz lead to S-T exciton annihilation as a result of triplet exciton accumulation. S-T annihilation kinetics results in monoexponential decay of the fluorescence kinetics and manifests itself as a decrease of the singlet exciton lifetime. The calculated time-independent S-S and S-T exciton annihilation rates strongly support the conclusion that the processes are controlled by the interchain diffusion of singlet excitons. Despite the low efficiency of S-T annihilation compared to that of S-S annihilation, it has a substantial effect on the singlet exciton lifetime due to a relatively long triplet lifetime (60 mu s). Thus, even optical excitation with low fluence at high pulse repetition rate creates a significant concentration of triplet states that efficiently quenches singlet excitons.
Subject Chemistry
Physics and Astronomy
ISBN/ISSN/Other ISSN: 1098-0121

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