Multicolored, Low-Voltage-Driven, Flexible Organic Electrochromic Devices Based on Oligomers

Flexible Composite Electrochromic Device with Long-Term Bistability Based on a Viologen Derivative and Prussian Blue

Viologen and Prussian blue (PB) exhibit good electrochromic properties, but certain limitations still exist. To improve the electrochromic properties of viologen, a viologen derivative 1,1'-bis(4-(bromomethyl)benzyl)-[4,4'-bipyridine]-1,1'-diium hexafluorophosphate (BBDV) was synthesized, and its electrochromic properties were investigated. Additionally, a flexible composite electrochromic device (FC-ECD) was prepared by using BBDV and PB as active materials. The structure of the FC-ECD was PET-ITO/gel electrolyte-BBDV/PB/PET-ITO. The applied voltage required for the FC-ECD was found to be lower than that of the ECD based on BBDV(FBBDV-ECD). Compared to FBBDV-ECD, FC-ECD exhibited a higher optical contrast (71.42%) and cyclic stability (89.51%). The FC-ECD exhibited multicolor changes under different applied voltages (ranging from -2.0 to +1.6 V). Especially, the color of the FC-ECD remained stable for 14 h after the removal of the applied voltage.

The Flexible Electrochromic Device That Turns Blue Under Both Positive and Negative Application Voltages

Using the photocurable electrolyte solution containing viologen derivative 1,1′-bis- (4-vinylbenzyl)-4,4′-bipyridinium dihexafluorophosphate (EV2+•2PF6−) and its composite of EV2+•2PF6− and triphenylamine derivative N,N′-di(4-((3-(triethoxysilyl)-propyl)imino)methyl)phenyl-N,N′-diphenyl-4,4′-biphenyldiamine (TPB-PSSO) as the electrochromic active layer, respectively, the flexible electrochromic devices (FECDs) were prepared by photocurable technology. The device structure was PET-ITO/photocurable electrolyte solution/PET-ITO. The electrochromic properties of FECDs were investigated. The results show that the FECDs can all undergo a reversible color change, especially the PET-ITO/photocurable electrolyte solution-composite/PET-ITO can undergo polychromatic transition. The FECD based on EV2+•2PF6− can reversibly change between colorless and deep blue, and the FECD based on the composite of TPB-PSSO-EV2+•2PF6− can reversibly change between black blue, light yellow, and sky blue.

A fast-response electrochromic device based on a composite gel film comprising triphenylamine derivatives and WO3

The WO₃/TPB-PSSO-based composite device containing TPB-PSSO and WO₃ exhibits fast-response, rich color changes, and good cycling stability.

Multicolored Cathodically Coloring Electrochromism and Electrofluorochromism in Regioisomeric Star-Shaped Carbazole Dibenzofurans

In this work, a series of fluorescent cathodically coloring electrochromic (EC) small molecules o-, m-, and p-DBFDCz with 3,5-di(9H-carbazol-9-yl)benzene (DCz) linked to dibenzofuran (DBF) at different substitutional positions were synthesized and fully characterized. These compounds are electroactive and undergo quasi-reversible two-step single-electron reduction generating radical anions and dianions. The absorptions of o-, m-, and p-DBFDCz in the neutral states lie in the UV region (λ_onset ≈ 350 nm), showing high transparency, while the absorption of their reduced states can be largely tuned across the visible region through driving voltage and substitutional positions. Initially generated spectroelectrochemically radical anions show absorption in the short-wavelength region of ∼380-500 nm with weak broad absorptions at longer wavelengths. On further reduction, these bands disappear on the cost of growing intense bands from dianions at longer wavelengths of 500-700 nm with some tail absorptions in the shorter-wavelength region. This renders the colors of the EC devices based on these materials, which are changed from green to red, yellow to magenta, and light to deep blue for o-, m-, and p-DBFDCz, respectively, covering four legs of the L*a*b* color space. Besides excellent optical contrast (>90%) and high coloration efficiency (up to 504 cm² C^-1), the fluorescence observed in solution of neutral o-, m-, and p-DBFDCz can be modulated between the fluorescence and quenched states by direct electrochemical redox reactions. Both EC and electrofluorochromic (EFC) processes are reversible on cycling. This research demonstrates the feasibility of developing multifunctional EC/EFC materials with multicolored electrochromism through exploiting electrochemical properties of traditional fluorescent small molecules.

Chemical bath deposition of transparent ZnO films incorporated with erythrosine B molecules and their synergetic electro/photochromic properties

Synergetic electro/photochromism was observed in transparent erythrosine B/ZnO hybrid films fabricated by a chemical bath deposition method.

Dual-colored 4,4′,4′′,4′′′-(cyclobutane-1,2,3,4-tetrayl)-tetrabenzoate electrochromic materials with large optical contrast and coloration efficiency

This paper reports novel ester-containing electrochromic materials, 4,4′,4′′,4′′′-(cyclobutane-1,2,3,4-tetrayl)tetrabenzoate derivatives, with dual-colored electrochromism, high color contrast and coloration efficiency.