In Situ Spectroscopic Analysis of Sub‐Second Switching Polymer Electrochromes

Abstract

As electrochromic polymers can switch with a high transmittance contrast in the sub‐second time frame, an analytical tool to rapidly probe the electrochemically‐induced optical transition is required for characterization of these materials for electronic displays and smart windows. A novel technique is described to synchronize the electrochemical and optical measurements by utilizing an external trigger to facilitate coordinated communication between the potentiostat, which applies a voltage to the electrode supported electrochromic polymers, and the optical spectrometer that records the induced optical transitions. By using a spectrometer containing a photodiode array detector, these measurements are capable of rapid data acquisition to track the electrochromic change in the polymer films, with as many as 500 spectra captured during a one‐second switch of the polymer from a colored, neutral to highly transmissive state. Additionally, with this rapid, full‐spectral measurement, it is possible to trace the temporal evolution of the electrochromic change to determine the presence of intermediate color tones, as well as their duration. Here, three polymers are shown, ECP‐Magenta, ECP‐Green, and ECP‐Black, which obtain high transmittance contrast between 40 to 50 Δ%T, with sub‐second switching times measured in the range of 400 to 700 ms, demonstrating their potential for use in electrochromic windows and displays where rapid transitions are desired.

Fast Switching Water Processable Electrochromic Polymers

“…38 Rather than monitoring only the transmittance change at one single wavelength, fast switching polymer films of WS-ECP-Blue-A-acid and WS-ECP-Blue-R-acid were also subjected to a technique, wherein the electrochromic properties are evaluated by associating a time parameter with a full visible spectrum change during the electrochromic transition. 51 Using a spectrophotometer with a fiber-optic cable coupled to a light source and a photodiode array detector, this measurement is capable of rapid data acquisition to track the electrochromic change in the polymer films across the visible region simultaneously. It is important to note that this absorption/ transmission profile is not a typical spectroelectrochemical experiment in which the electrochromic film is monitored at a steady-state (i.e., constant applied potential).…”

Poly(fluorene-co-thiophene)-based ionic transition-metal complex polymers for solar energy harvesting and storage applications

“…In situ spectroelectrochemical studies 31 were employed to elucidate the properties of the polymer backbone oxidized and iTMC chromophore reduced states, as these states were anticipated to be the products of photoinduced charge separation. For spectroelectrochemical studies, thin lms of the polymers were prepared on ITO-coated glass transparent working electrodes by drop-casting either from acetone (PFT-Ru and PF2T-Ru) or tetrahydrofuran solutions.…”

Relax: A Sterically Relaxed Donor–Acceptor Approach for Color Tuning in Broadly Absorbing, High Contrast Electrochromic Polymers

“…Throughout the recent decade, π-conjugated electrochromic polymers (ECPs) have demonstrated their facility in color tuning as a result of structural modification of the polymer’s repeat unit, , color mixing via solution blending of primary colored ECPs, , and device architectures which allow color control of EC films independently of one another. , As ECPs are typically solution coated as films which can be imbibed with supporting electrolyte, they exhibit the ability to switch with high contrast more rapidly than metal oxides, with typical times on the order of a second for small (cm 2 ) devices . Along with the ability to tune the optical properties, ECPs can be processed into thin films using roll-to-roll techniques, , and modification of material solubility is achievable via postprocessing functionalization. , Methods also exist to enable ECP aqueous processing with subsequent conversion to solvent-resistant forms, yielding fast electrochromic switching kinetics. , …”

“…20,21 As ECPs are typically solution coated as films which can be imbibed with supporting electrolyte, 22 they exhibit the ability to switch with high contrast more rapidly than metal oxides, with typical times on the order of a second for small (cm 2 ) devices. 23 Along with the ability to tune the optical properties, ECPs can be processed into thin films using roll-to-roll techniques, 24,25 and modification of material solubility is achievable via postprocessing functionalization. 26,27 Methods also exist to enable ECP aqueous processing with subsequent conversion to solventresistant forms, yielding fast electrochromic switching kinetics.…”