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Two-dimension covalent organic frameworks (2D COFs) are porous materials with the interlayer π-π interaction and excellent optoelectronic properties. Their adjustable porous structure and designable molecular structure endow them unlimited possibilities in the field of optoelectronic materials and other functional materials. In this paper, 2D COF electrochromic films were prepared by solvothermal synthesis method with different amounts of functionalized carbon nanotubes (FCNT) loading to improve their conductivity. The morphology characterization of COFDAAQ-TFP reveals its intertwined nanofiber structure. The electrochromic performance of COFDAAQ-TFP film shows that the color of COFDAAQ-TFP and FCNT-COFDAAQ-TFP have a reversible transformation from orange to dark brown during the redox process. When the loading amount of FCNT is 1%, FCNT-COFDAAQ-TFP exhibits best electrochromic properties, which has a contrast of 0.358 and coloring time of 5.7 s. Relative to COFs, FCNT-COF has enhanced contrast and stability, which is a potential electrochromic material in many fields such as smart window and smartphone back case.

In this paper, we designed a novel organic-inorganic nanohybrid electrochromic material through tethering polyaniline and gold colloids with an interfacial coordinate bond. The enhanced electrochemical and electrochromic properties were expected owing to the high conductivities of the gold colloids and strong interfacial interaction between the organic phase and inorganic phase. The water-dispersible polyaniline-gold (PANI-Au) nanohybrids were synthesized successfully through grafting copolymerization of aniline with p-aminothiophenol (PATP) functionalized gold colloids in an aqueous system using a macromolecular acid, poly(styrene sulfonate) (PSS) as the dopant agent. The structures, morphologies, and electrochemical and electrochromic properties of PANI-Au nanohybrids were characterized by the UV–vis, FTIR, Raman spectrometers, SEM, and electrochemical working station, respectively. The results show that through incorporating gold nanoparticles into the PANI matrix with the interfacial coordinate bond, PANI-Au nanohybrids possess uniform nanoparticles morphologies with diameter ~180 nm. The electrochemical activity and the charge transfer process of PANI were enhanced, which is proved by the CV test and EIS analysis. As the results, the PANI-Au nanohybrids can switch at relatively lower potentials and give a higher optical contrast as comparison with neat PANI: PSS. With ~1.4 wt% Au loading amount, the contrast of PANI-Au nanohybrid is 0.97, which is much higher than 0.76 of PANI: PSS. The coloration and bleaching time are also shortened from 13.4 s and 8.9 s for PANI: PSS to 8.3 s and 7.6 s for PANI-Au-c, respectively.

Inspired by hydrothermal synthesis of inorganic crystallites, we apply one-step hydrothermal polymerization to directly grow polyaniline on fluorine-doped tin oxide (FTO) substrate. In contrast to classical procedure that requires long reaction times and low temperature, hydrothermal polymerization allows for only 3 h under hydrothermal condition. Investigation of the morphology via SEM suggests that PANI fiber aggregates uniformly on FTO substrate. The PANI film was used as electrochromic layer in an electrochromic device and the obtained PANI film shows high electrochromic performance. We believe that this study provided a novel way to directly grow PANI on FTO substrate and, thus, has some impact on the applications of other conjugated polymers in electrochromic and electrochemical devices.

Covalent organic framework is a designable and versatile platform for preparation of various functional materials including conventional gas adsorption and separation materials, catalysis matrix, and photoelectric materials, etc. The covalent organic framework with redox building block and conjugated molecular structure can be viewed as a conjugated polymer with ordered porous structure. In this paper, we synthesized a Schiff base type conjugated organic framework (COF) by a solvothermal method in a common Teflon-lined stainless steel autoclave. The reversible reaction of dynamic imine bonds in solvothermal process induces the morphology transform of COF from nanoparticle to nanofiber. Besides of its structure, morphology, nanofiber-formation mechanism and electrochemical properties, the electrochromic properties of COF were investigated for the first time. Owing to the redox building block of triphenylamine, the COF possesses reversibly electrochromic behavior caused by reversibly redox reaction and band gap change of triphenylamine unit. Under step potentials between −2.5 V and 2.5 V, the COF can switch between bright yellow color and brown color. The stability test shows that the device can reversibly switch with stable contrast after slight decay at the initiated cycles. In consideration of abundant options of building units with redox feature, the COF based electrochromic materials with rich color and novel properties can be expected.

Poly(styrene sulfonate) (PSS) tethered polyhedral oligomeric silsesquioxane (POSS-PSS) was synthesized and used as star-like dopant for the preparation of core–shell polyaniline/POSS-PSS (PANI/POSS-PSS) nanoparticles. The prepared aqueous emulsion shows good processibility and high stability. The electrochemical characteristics and electrochromic properties of PANI/POSS-PSS were studied. In comparison with polyaniline (PANI) doped with linear PSS dopant, the star-like POSS-PSS dopant renders PANI/POSS-PSS-based electrochromic device higher optical contrast and faster switching speed owing to the faster ion transportation resulting from the porous morphology of PANI/POSS-PSS.

A high-contrast complementary electrochromic device based on polyaniline (PANI) tethered polyhedral oligomeric silsesquioxane (POSS) (POSS-PANI) and poly(3,4-ethylenedioxythiophene)/poly(4-styrene sulfonic acid) (PEDOT:PSS) is assembled. The electrochromic properties, cyclic voltammetry behavior and coloration efficiency of the device are studied. Due to the loosely packed structure, POSS-PANI gives rise to a significantly higher electrochromic contrast, coloration efficiency and faster switching speed than PANI. Despite its high contrast, the combination of POSS-PANI with PEDOT:PSS still shows synergy in terms of contrast enhancement, which can be attributed to the additional driving force for the diffusion of dopants into PEDOT:PSS provided by the dedoping of POSS-PANI.

In this paper we report a high-contrast complementary electrochromic device based on polyaniline-tethered polyhedral oligomeric silsesquioxane (POSS-PANI) and tungsten oxide (WO3). The electrochromic properties, cyclic voltammetry behavior and coloration efficiency of the device are studied. Due to the loosely packed structure of POSS-PANI, it possesses more accessible doping sites and hence gives rise to a significantly higher electrochromic contrast than polyaniline (PANI). Furthermore, the replacement of PANI with POSS-PANI as the complementary layer for WO3 leads to an enhanced complementary effect, for which the underneath mechanism is also discussed.