Mass Diffusion Coefficient and Soret Coefficient of <i>o</i>-Dichlorobenzene Solutions of PCBM and [60]Fullerene by the Soret Forced Rayleigh Scattering Method

Matsuura, Hiroaki; Iwaasa, Shintaro; Nagasaka, Yuji

doi:10.1021/acs.jced.5b00609

Cited by 12 publications

(14 citation statements)

References 49 publications

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“…Therefore, diffusion must also play an important role on the domain size. Although data on diffusivity coefficients for OPV materials in solution is very limited due to the lack of suitable measurement techniques, [37] there is still much insight to be gained from a qualitative understanding of the interplay between diffusion and evaporation. Here, we derive the temperature dependence of Bi m to account for diffusion.…”

Section: Discussionmentioning

confidence: 99%

“…We hypothesize that the observed composition change with thickness is due to the differential diffusivities of the polymer and PCBM molecules in the context of the Soret effect. [37] Evaporative cooling at the drying front induces a thermal gradient, which may cause PCBM to preferentially diffuse from the solution reservoir resulting in higher PCBM content in the final film. In thicker films, a slower shearing speed increases film drying time, increasing the magnitude of the effect.…”

Section: Photophysical Propertiesmentioning

confidence: 99%

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Tuning domain size and crystallinity in isoindigo/PCBM organic solar cells via solution shearing

Zhou

et al. 2017

Organic Electronics

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Despite having achieved the long sought-after performance of 10% power conversion efficiency, high performance organic photovoltaics (OPVs) are still mostly constrained to lab scale devices fabricated by spin coating. Efforts to produce printed OPVs lag considerably behind, and the sensitivity to different fabrication methods highlights the need to develop a comprehensive understanding of the processing-morphology relationship in printing methods. Here we present a systematic experimental investigation of a model low bandgap polymer/fullerene system, polyisoindigo thienothiophene/PC 61 BM, using a lab-scale analogue to roll-to-roll coating as the fabrication tool in order to understand the impact of processing parameters on morphological evolution. We report that domain size and polymer crystallinity can be tuned by a factor of two by controlling the temperature and coating speed. Lower fabrication temperature simultaneously decreased the phase separation domain size and increased the relative degree of crystallinity in those domains, leading to improved photocurrent. We conclude that domain size in isoindigo/PCBM is dictated by spontaneous phase separation rather than crystal nucleation and growth. Furthermore we present a model to describe the temperature dependence of domain size formation in our system, which demonstrates that morphology is not necessarily strictly dependent on the evaporation rate, but rather on the interplay between evaporation and diffusion during the printing process.

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Section: Discussionmentioning

confidence: 99%

Section: Photophysical Propertiesmentioning

confidence: 99%

Tuning domain size and crystallinity in isoindigo/PCBM organic solar cells via solution shearing

Zhou

et al. 2017

Organic Electronics

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“…In spite of these complications, some books or reviews present the theory of thermodiffusion in binaries in terms of molar concentrations [4,26], as well as some experimentalists report binary Soret coefficients using these concentration units [27,28]. However, a detailed examination shows that in these works it is implicitly assumed: (i) That the dependence of c t on temperature can be neglected.…”

Section: Molar Concentrationsmentioning

confidence: 99%

“…Solving Eq. ( 13) leads to the so-called exponential depletion law [29], which is the starting point of many experimental works reporting Soret coefficients, in particular of macromolecules, biomolecules or colloidal particles [27,28,29,30]. In these cases the assumptions mentioned above typically hold.…”

Section: Molar Concentrationsmentioning

confidence: 99%

Definition of frame-invariant thermodiffusion and Soret coefficients for ternary mixtures

Zárate

2019

Eur. Phys. J. E

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The definition of the Soret coefficient of a binary mixture includes a concentration prefactor, x(1 − x) when mol fraction x is used, or w(1 − w) when mass fraction w is used. In this paper the physical reasons behind this choice are reviewed, emphasizing that the use of these prefactors makes the Soret coefficient invariant upon change in the reference frame, either mass or molar. Then, it is shown how this invariance property can be extended to ternary mixtures by using an appropriate concentration prefactor in matrix form. The work is completed with some considerations of general non-isothermal diffusion fluxes, binary limits of the concentration triangle, selection of the dependent concentration in a ternary mixture, use of molar concentrations and, finally, extension to multi-component mixtures.

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“…To contribute to the understanding of the mass transport in PEMs, in our laboratory we have tried to measure the diffusion coefficient in PEMs by the infrared Soret forced Rayleigh scattering (IR-SFRS) method (Sakai et al, 2012), which has been developed to apply the optical holographic grating technique of the Soret forced Rayleigh scattering (SFRS) or the thermal diffusion forced Rayleigh scattering (TDFRS) employing visible light lasers (Hayashida and Nagasaka, 1997;Nagasaka, 2006a, 2006b;Niwa et al, 2009;Matsuura et al, 2015;Matsuura and Nagasaka, 2017;Matsuura and Nagasaka, 2018) to the measurement of solutions in PEMs. The feature of the IR-SFRS technique includes the following: 1) Mass transport in PEMs is induced by a carbon dioxide (CO 2 ) laser without dye for laser absorption, and contactless detection of the mutual diffusion is performed by another laser (probing laser).…”

Section: Introductionmentioning

confidence: 99%

Development of measurement technique of mass diffusion coefficient of aqueous methanol solutions in polymer electrolyte membranes based on infrared Soret forced Rayleigh scattering method using single crystal diamond window in a sample cell

Matsuura

Tokuda

Nagasaka

2018

JTST

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We have developed an experimental apparatus for the measurement of diffusion coefficient of aqueous methanol solutions in a polymer electrolyte membrane (PEM) for direct methanol fuel cells (DMFCs), based on the infrared Soret forced Rayleigh scattering (IR-SFRS) method. Because mass transport phenomena in PEMs play significant roles, evaluation and understanding of the mass diffusion in PEMs is important. In the present study, we developed a new sample cell using a single crystal diamond window, which transmits both the heating laser with the wavelength of 9.714 m and the probing laser with the wavelength of 639 nm. The heating wavelength was selected from the emission range of a valuable-wavelength carbon dioxide laser to utilize the absorption of methanol due to CO stretching. By using a single crystal diamond window, the scattered light of the probing laser generated at the window material which causes unpreferable effects on detection signals was reduced to about 1/150, compared to a polycrystalline diamond window. To evaluate the validity of the measurement system, we carried out experiments on the aqueous methanol solutions at a temperature of T = 298.2 K. The mass diffusion coefficient of the aqueous methanol solution with the mole fraction of 0.7 measured in the present study agreed with the measured values by the diaphragm cell technique within the relative standard uncertainty of 8.9%. After the validation, we performed experiments on three concentrations of aqueous methanol solutions in a PEM of Nafion 117 at T = 298.2 K. The mass diffusion in Nafion was observed in several hundreds of milliseconds. We obtained the mass diffusion coefficient with the relative standard uncertainties of 2.5-5.3%, depending on the methanol concentration. The mass diffusion coefficient in Nafion 117 was smaller than that of bulk aqueous methanol solutions, and increased with the increase in the methanol mole fraction.Keywords : Diffusion coefficient, Mass transport in membranes, Aqueous methanol solutions, Polymer electrolyte membrane (PEM), Nafion, Direct methanol fuel cell (DMFC), Optical measurement Matsuura, Tokuda and Nagasawa, Journal of Thermal Science and Technology, Vol.13, No.1 (2018)

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Mass Diffusion Coefficient and Soret Coefficient of o-Dichlorobenzene Solutions of PCBM and [60]Fullerene by the Soret Forced Rayleigh Scattering Method

Cited by 12 publications

References 49 publications

Tuning domain size and crystallinity in isoindigo/PCBM organic solar cells via solution shearing

Tuning domain size and crystallinity in isoindigo/PCBM organic solar cells via solution shearing

Definition of frame-invariant thermodiffusion and Soret coefficients for ternary mixtures

Development of measurement technique of mass diffusion coefficient of aqueous methanol solutions in polymer electrolyte membranes based on infrared Soret forced Rayleigh scattering method using single crystal diamond window in a sample cell

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