Organic Electronics for Electrochromic Materials and Devices. Hong Meng

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Organic Electronics for Electrochromic Materials and Devices - Hong Meng


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      Source: Kraft [25].

      In addition, when insightfully considering the injected/ejected charge Qd, we can find it in fact to consist of three part: faradaic charge QF associated with doping/de‐doping, capacitive charge QC due to the capacitive nature of the ECD, and parasitic charge QP associated with electrolyte/impurity reactions. Among them, the faradaic charge is the source of redox activity leading to chromic change actually. Therefore, Fabretto et al. reported a new technique for measuring CE by extracting the faradaic charge from the total charge and calculated the only faradaic charge‐based CE value [29]. As we discussed, the total charge flow is simply the addition of the three individual charge flows and is given by

upper Q Subscript d Baseline equals upper Q Subscript upper F Baseline plus upper Q Subscript upper C Baseline plus upper Q Subscript upper P

      where the parasitic current was a small component (approximately <2%) compared with the other two and therefore can be ignored. Then the time–evolution total current flow can be described as following:

upper I Subscript d Baseline left-parenthesis t right-parenthesis equals upper I Subscript upper F Baseline left-parenthesis t right-parenthesis plus upper I Subscript upper C Baseline left-parenthesis t right-parenthesis equals StartFraction n upper F upper A normal upper C 0 upper D Superscript 1 slash 2 Baseline Over pi EndFraction t Superscript negative 1 slash 2 Baseline plus upper I 0 normal e Superscript negative t slash upper R upper C Baseline equals k t Superscript negative 1 slash 2 Baseline plus upper I 0 normal e Superscript negative t slash upper R upper C

      where n is the number of electrons transferred per molecule, F is the Faraday constant (96 500 C/mol), A is the electrode area (cm2), C0 is the concentration of species in the bulk solution (mol/cm3), D is the apparent diffusion coefficient (cm2/s), t is time in seconds, I0 is the maximum current flow at t = 0, R is the cell resistance, and C is the double layer capacitance. Then fitting the experimental data to this equation and substituting the constant k, at last, a plot of the time–evolution faradaic current will be obtained, and the corresponding faradic‐corrected CEs can be calculated. Usually, the faradic‐corrected CEs are larger than the uncorrected results, because the total charge ingress/egress (i.e. Qd) is larger than the faradic charge (i.e. QF).

      1.3.4 Optical Memory

Graphs depict the open-circuit memory tests of PBOTT-BTD spray coated on an ITO-coated glass slide in 0.1 M TBAPF6/ACN at 423 nm: (a) short- and (b) long-term performance.

      Source: Li et al. [21].

      1.3.5 Stability

Graphs depict the charge density (a) and transmittance (b) variation curves of ECD with the cycle number K : 1000.

      Source: Wei et al. [30].

Schematic illustration of the recommended testing guidelines for EC windows for exterior architectural applications.

      Source: Lampert et al. [31].


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