Ultrafast dynamics of singlet-singlet and singlet-triplet exciton annihilation in poly(3-2 '-methoxy-5 '-octylphenyl)thiophene films

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title = "Ultrafast dynamics of singlet-singlet and singlet-triplet exciton annihilation in poly(3-2 '-methoxy-5 '-octylphenyl)thiophene films",
abstract = "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.",
author = "Yuri Zaushitsyn and Kim Jespersen and Leonas Valkunas and Villy Sundstr{\"o}m and Arkady Yartsev",
note = "The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Chemical Physics (S) (011001060)",
year = "2007",
doi = "10.1103/PhysRevB.75.195201",
language = "English",
volume = "75",
journal = "Physical Review B",
issn = "2469-9950",
publisher = "American Physical Society",
number = "19",