Dynamics in the BMIM PF<sub>6</sub>/acetonitrile mixtures observed by femtosecond optical Kerr effect and molecular dynamics simulations

Polok, Kamil; Beisert, Matthieu; Świątek, Adam; Maity, Nishith; Piątkowski, P.; Gadomski, W.; Miannay, François-Alexandre; Idriss, Hicham

doi:10.1039/d0cp03847d

Cited by 5 publications

(7 citation statements)

References 108 publications

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“…Indeed, in our recent optical Kerr effect study of a similar BmimPF 6 –ACN mixture (bulk solvent without the dye), we showed that admixing the IL to acetonitrile results in a significant slowdown of the mixture dynamics. We observed that already at X IL = 0.05, the slowest relaxation time is 18 ps and grows to 1.6 ns for the pure IL . In the case of systems with the dye, these relaxation times might differ in the cybotactic region compared to the bulk; however, they clearly show that solvation can be involved in τ 3 .…”

Section: Resultsmentioning

confidence: 75%

“…We observed that already at X IL = 0.05, the slowest relaxation time is 18 ps and grows to 1.6 ns for the pure IL. 65 In the case of systems with the dye, these relaxation times might differ in the cybotactic region compared to the bulk; however, they clearly show that solvation can be involved in τ 3 . In our case, even for the pure IL, we cannot see any evidence of solvation in the DAS associated with τ 4 , while it is clearly observed for τ 3 for the pure IL and all the mixtures.…”

Section: Discussion Of Four Global-analysis Time Constantsmentioning

confidence: 97%

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Effect of the Mixture Composition of BmimBF₄–Acetonitrile on the Excited-State Relaxation Dynamics of a Solar-Cell Dye D149: An Ultrafast Transient Absorption Study

et al. 2021

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The excited-state relaxation dynamics of D149, one of the metal-free substituted indoline dyes used in dye-sensitized solar cells, is studied in the whole composition range of the 1butyl-3-methylimidazolium tetrafluoroborate (BmimBF 4 )−acetonitrile binary mixture by using time-integrated absorption, emission, and time-resolved transient absorption (TA) spectroscopies. The comparative analysis of absorption and emission spectra indicates that the value of Stokes shift reduces monotonically with decreasing mixture polarity. The global analysis of timeresolved TA spectra indicates the presence of four different time components related to different processes in the excited state of the dye. Importantly, the observed timescales are highly sensitive to composition, polarity, and viscosity of the binary mixture. Increase of viscosity and decrease of polarity observed for increasing ionic liquid (IL) content in the mixture lead to overall increase in the emission lifetime (S 1 −S 0 ) of D149. At a lower IL mole fraction (X IL = 0.1), the emission lifetime shows a minimum that can be traced back to the change from the situation in which the local environment of the dye is dominated by the interactions in acetonitrile to that in which it is dominated by those in BmimBF 4 . This also is reflected in the occurrence of a minimum in relative quantum yield in the same range of X IL . The origin of the other moderately long-time component (33 ps in ACN-120 ps in BmimBF 4 ) is still debatable; however, for pure IL and all the mixtures, the composition dependence of this timescale is similar to that of the longest emission lifetime.

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Section: Resultsmentioning

confidence: 75%

Section: Discussion Of Four Global-analysis Time Constantsmentioning

confidence: 97%

Effect of the Mixture Composition of BmimBF₄–Acetonitrile on the Excited-State Relaxation Dynamics of a Solar-Cell Dye D149: An Ultrafast Transient Absorption Study

et al. 2021

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“…Lastly, τ 4 can be attributed to the decay process of the charge transfer (CT) excited state. Furthermore, considering the presence of very slow solvation dynamics time components (especially in pure ILs and at higher X IL mixtures) found in previous studies, , we cannot discount the possibility of the solvation process contributing to both τ 3 and τ 4 as well.…”

Section: Resultsmentioning

confidence: 76%

“…However, in essence, all of the global analysis time components can be viewed as mixed-time components, incorporating multiple excited state processes. For instance, both τ 1 and τ 2 may involve solvation dynamics ,,− alongside intramolecular vibrational relaxation (IVR), dye aggregation, and the ultrafast decay of the locally excited (LE)/Franck–Condon state, while τ 3 may primarily involve excited state vibrational relaxation and ultrafast twisting. Lastly, τ 4 can be attributed to the decay process of the charge transfer (CT) excited state.…”

Section: Resultsmentioning

confidence: 99%

Effect of Mixture Composition on the Photophysics of Indoline Dyes in Imidazolium Ionic Liquid-Molecular Solvent Mixtures: A Femtosecond Transient Absorption Study

Maity,

Polok,

Piatkowski

et al. 2024

J. Phys. Chem. B

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We conducted a study on the photophysics of three indoline dyes, D102, D149, and D205, in binary mixtures of ionic liquids (IL) and polar aprotic molecular solvents (MS). Specifically, we examined the behavior of these dyes in IL-MS mixtures containing four different imidazolium-based ILs and three different polar aprotic MSs. Our investigation involved several techniques, including stationary absorption and emission measurements, as well as femtosecond transient absorption (TA) spectroscopy. Through our analysis, we discovered a peculiar behavior of several photophysical properties at low IL mole fractions (0 < X IL < 0.2). Indeed, in this range of mixture composition, the absorption maximum wavelength decreases noticeably, while the emission maximum wavelength and the Stokes shift, expressed in wavenumbers, reach a maximum. while a minimum occurs in the relative quantum yield and the excited state lifetime. These results indicate that the solvation of dye undergoes a large change in this range of mixture composition. We found that, at high ionic liquid content, the excited relaxation times are correlated with the high viscosity, while at low content, it is the polarity of the solvent that influences the behavior of the excited relaxation times. At a mixture composition of around 0.10, the behavior of the photophysical properties of the studied IL-MS mixtures indicates a crossover between situations where the solvation is dominated by that of ions and that dominated by the solvent.

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“…We observed that already at XIL = 0.05, the slowest relaxation time is 18 ps and grows to 1.6 ns for pure IL. 65 In the case of systems with the dye, these relaxation times might differ in the cybotactic region compared to the bulk; however, they clearly show that solvation can be involved in 3 . In our case even for pure IL we cannot see any evidence of solvation in the DAS associated with 4 , while it is clearly observed for 3 for pure IL and all the mixtures.…”

Section: Discussion Of Four Global Analysis Time Constantsmentioning

confidence: 98%

The Effect of the Mixture Composition of BmimBF4-Acetonitrile on the Excited State Relaxation Dynamics of a Solar Cell Dye D149: An Ultrafast Transient Absorption Study

Maity

Piątkowski²,

Polok³

et al. 2021

Preprint

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It has been recognized that the understanding of the photo physic of the dyes used in solar cells in an important step in improving their efficiency. Certainly using ionic liquid as an electrolyte is a good solution as it stabilizes the excited state of the dye, however, because of the high viscosity, the diffusion of the components of the solar cell (dye, electrolyte, the chosen redox couple) is very low and has consequences on the other processes (Forward and backward processes). One of the ideas, is to modulate the viscosity of the ionic liquid by mixing the ionic liquid with a solvent. The goal then of this work is to quantify the mixture composition dependence of the excited state relaxation times. Other studies should be carried out to quantify the mixture dependence on the time characteristics of other processes (charge injection, collection etc.) to optimize the working optimal conditions of the solar cell. Following this goal, the present study is devoted to characterize the relaxation time of in the whole mixture composition of BmimBF4 and acetonitrile and in the neat components. For the first time, the decay relaxation times of the first excited electronic state of D149 dye, as obtained by transient absorption spectroscopy (TAS). These relaxation times are monitored by a gradual change of the local structure around a dye, from the one dominated by the interionic interactions, high viscosity and low polarity (as quantified by the static dielectric constant) in BmimBF4 to the one that is dominated by dipole-dipole interactions, low viscosity and high polarity in acetonitrile.<br>

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Dynamics in the BMIM PF₆/acetonitrile mixtures observed by femtosecond optical Kerr effect and molecular dynamics simulations

Abstract: We have performed the measurements of the optical Kerr effect signal time evolution up to 4 ns for a mixture of 1-alkyl-3-methyl-imidazolium hexafluorophosphate (BMIM PF6 ) ionic liquid and acetonitrile...

Cited by 5 publications

References 108 publications

Effect of the Mixture Composition of BmimBF₄–Acetonitrile on the Excited-State Relaxation Dynamics of a Solar-Cell Dye D149: An Ultrafast Transient Absorption Study

Effect of the Mixture Composition of BmimBF₄–Acetonitrile on the Excited-State Relaxation Dynamics of a Solar-Cell Dye D149: An Ultrafast Transient Absorption Study

Effect of Mixture Composition on the Photophysics of Indoline Dyes in Imidazolium Ionic Liquid-Molecular Solvent Mixtures: A Femtosecond Transient Absorption Study

The Effect of the Mixture Composition of BmimBF4-Acetonitrile on the Excited State Relaxation Dynamics of a Solar Cell Dye D149: An Ultrafast Transient Absorption Study

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Dynamics in the BMIM PF6/acetonitrile mixtures observed by femtosecond optical Kerr effect and molecular dynamics simulations

Abstract: We have performed the measurements of the optical Kerr effect signal time evolution up to 4 ns for a mixture of 1-alkyl-3-methyl-imidazolium hexafluorophosphate (BMIM PF6 ) ionic liquid and acetonitrile...

Cited by 5 publications

References 108 publications

Effect of the Mixture Composition of BmimBF4–Acetonitrile on the Excited-State Relaxation Dynamics of a Solar-Cell Dye D149: An Ultrafast Transient Absorption Study

Effect of the Mixture Composition of BmimBF4–Acetonitrile on the Excited-State Relaxation Dynamics of a Solar-Cell Dye D149: An Ultrafast Transient Absorption Study

Effect of Mixture Composition on the Photophysics of Indoline Dyes in Imidazolium Ionic Liquid-Molecular Solvent Mixtures: A Femtosecond Transient Absorption Study

The Effect of the Mixture Composition of BmimBF4-Acetonitrile on the Excited State Relaxation Dynamics of a Solar Cell Dye D149: An Ultrafast Transient Absorption Study

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Dynamics in the BMIM PF₆/acetonitrile mixtures observed by femtosecond optical Kerr effect and molecular dynamics simulations

Effect of the Mixture Composition of BmimBF₄–Acetonitrile on the Excited-State Relaxation Dynamics of a Solar-Cell Dye D149: An Ultrafast Transient Absorption Study

Effect of the Mixture Composition of BmimBF₄–Acetonitrile on the Excited-State Relaxation Dynamics of a Solar-Cell Dye D149: An Ultrafast Transient Absorption Study