Revealing ultrafast relaxation dynamics in six-thiophene thin film and single crystal

Zhao, Tianyu; Kloc, Christian; Ni, Wenjun; Sun, Licheng; Gurzadyan, Gagik G.

doi:10.1016/j.jphotochem.2020.112920

Cited by 6 publications

(8 citation statements)

References 56 publications

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“…The lifetimes of singlet excited states obtained from global fit are similar to 400 nm: τ 1 = 4.9 ps and τ 2 = 110 ps. From TA spectra, we cannot get any sign of polaron, charges, or ionization, as was observed in our previous studies with similar organic films. − …”

Section: Resultsmentioning

confidence: 55%

Switching Pathways of Triplet State Formation by Twisted Intramolecular Charge Transfer

Zhou

Lunchev

et al. 2021

J. Phys. Chem. B

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With the aim of constructing efficient photoelectric organic materials, a pyrido[3,2-g]quinoline derivative named LA17b has been synthesized, and its photodynamic relaxation processes in solvents and films were studied by time-resolved fluorescence and femtosecond transient absorption techniques. The steady-state fluorescence spectra show pronounced red-shift with the increase of the solvent polarity as well as in binary solvent hexane/ethanol by increasing ethanol concentration. However, the strong red-shift does not lead to quenching of the fluorescence. This is explained in terms of a twisted intramolecular charge transfer (TICT) state. The TICT state of LA17b in ethanol is highly emissive with a long fluorescence lifetime: 1.1 ns. TICT state was shown to play an important role in enhancement of intersystem crossing rate. TD-DFT calculations confirm the pathways of relaxation of locally excited state via TICT and triplet states. In films, the photodynamic properties are similar to that of LA17b in hexane and the TICT state vanishes due to the rigid environment. The obtained optical properties of this molecule suggest that it can be a promising candidate for various optoelectronic applications.

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Section: Resultsmentioning

confidence: 55%

Switching Pathways of Triplet State Formation by Twisted Intramolecular Charge Transfer

Zhou

Lunchev

et al. 2021

J. Phys. Chem. B

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“…In the film, the subsequent triplet−triplet annihilation (TTA), which results in the dramatic shortening of the triplet lifetime, is favored compared with that in the crystal. 38 In the ICZ single crystal, the ESA band peaking at S 1 −S N absorption 480 nm (Figure 3e) is broadened to the 450−750 nm range. The TA kinetics of this band has two decay components (Figure 3f): τ 1 = 1.7−2.8 ps and τ 2 = 20−33 ps.…”

Section: ■ Results and Discussionmentioning

confidence: 97%

“…Note that the triplet-state lifetime in the film is much shorter: τ = 2.1 μs (Figure S8). In the film, the subsequent triplet–triplet annihilation (TTA), which results in the dramatic shortening of the triplet lifetime, is favored compared with that in the crystal …”

Section: Resultsmentioning

confidence: 99%

Singlet Fission, Polaron Formation, and Energy Transfer in Indolo[3,2-b]carbazole Thin Films and Single Crystals

Zhao

Kloc

et al. 2021

J. Phys. Chem. C

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The ultrafast excited-state relaxation dynamics of indolo-[3,2-b]carbazole (ICZ) molecules were investigated in thin films and single crystals. In the ICZ film, singlet fission (SF) was directly observed both from the upper excited singlet states S N within 480−850 fs and from the upper vibrational levels of the singlet state S 1 within 6−11 ps, which fully suppressed the intramolecular charge transfer (CT) process in S 1 . In the ICZ crystal, the exciton relaxation through SF and polaron formation compete in the ultrafast timescale (<30 fs), which is accompanied by a thermally induced broadening of the S 1 −S N absorption band in the transient absorption spectra. The triplet-state lifetime is shortened from ICZ crystals (>1 ms) to films (2 μs) due to SF with subsequent triplet−triplet annihilation, suggesting the impact of well-structured crystallinity and molecular packing on the exciton transport dynamics. The efficient SF together with well-characterized energy transfer and CT properties of ICZ solids extends the usage of ICZ-core-based organic materials in photovoltaic and electrochemical applications.

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“…The prominent red-shift and broadening of the S 1 absorption are caused by J-aggregation and inhomogeneous broadening. The difference of the red-shift between the amorphous and crystalline films suggests the presence of extended nanoaggregates with a range of comparable states. − ,, The discrepancy between the absorption and excitation spectra in the wavelength range of 410–575 nm indicates that excitons’ relaxation is bypassing the fluorescence emissive state S 1 . The emission band is at 557 nm, and the fluorescence quantum yield Φ fl of the PhBDP crystalline film is measured to be 0.01.…”

Section: Resultsmentioning

confidence: 99%

Singlet Fission from Upper Excited States of Bodipy Crystalline Film and Single Crystal

Zhou

et al. 2022

J. Phys. Chem. C

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The well-known boron-dipyrromethene (bodipy) dyes have excellent photophysical and photochemical properties, which are significant for practical use in many fields. meso-Phenyl-substituted bodipy (PhBDP) as one of the most classical bodipy derivatives was investigated in the forms of amorphous film, crystalline film, and single crystal by using time-resolved fluorescence and femtosecond transient absorption techniques. The fluorescence of both PhBDP films is strongly quenched because of Jaggregation, which is randomly distributed in the amorphous film but well arranged in the crystalline film. In the crystalline film, the triplet states were populated from the upper excited singlet states (3.54 eV) of the nanoaggregates via singlet fission (SF) within 30 fs. Moreover, SF was also detected after excitation of the lower singlet states (2.58 eV) which are below the SF threshold (3.28 eV). This phenomenon was explained in terms of two-quantum absorption. However, in the amorphous film, the SF process was not observed, indicating the crucial impact of the nanoaggregate morphology on the formation of SF. In the single crystal, SF was also generated owing to the molecular slip-stacked packing which is optimal for the delocalization of excitation. It facilitates exciton fission and energy transfer between the neighboring PhBDP dimer moieties as well. Our findings of PhBDP solids provide a significant theoretical and experimental basis for exploring new SF systems. The prominent quenching, efficient SF, and well-characterized energy transfer of PhBDP solid expands the applications of PhBDP-based organic materials in optoelectronic devices.

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Revealing ultrafast relaxation dynamics in six-thiophene thin film and single crystal

Cited by 6 publications

References 56 publications

Switching Pathways of Triplet State Formation by Twisted Intramolecular Charge Transfer

Switching Pathways of Triplet State Formation by Twisted Intramolecular Charge Transfer

Singlet Fission, Polaron Formation, and Energy Transfer in Indolo[3,2-b]carbazole Thin Films and Single Crystals

Singlet Fission from Upper Excited States of Bodipy Crystalline Film and Single Crystal

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