Cellulose Nanocrystals/Poly(3,4-ethylenedioxythiophene) Photonic Crystal Composites with Electrochromic Properties for Smart Windows, Displays, and Anticounterfeiting/Encryption Applications

Abstract

Poly(3,-based electrochromic materials with low cost, room-temperature processing, energy conservation, and controllable color switching have attracted wide attention. However, they face challenges such as monotonous color change and slow switching responses, which have limited their applications. Besides, natural compounds have been rarely used in poly(3,4-ethylenedioxythiophene) (PEDOT) composites, making it challenging to produce green and sustainable PEDOT-based electrochromic devices. In this work, a chiroptical, electrochromic photonic crystal coating was fabricated through the co-assembly of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) with natural materials such as cellulose nanocrystals (CNCs), oxidized starch (OS), and tannic acid (TA). The hydrogen-bonding-based cross-linking network made by carbohydrate polymers and polyphenols endows the composite coating with good water and acid resistance and strong adhesion to the indium tin oxide (ITO) substrate. After H 2 SO 4 washing, the composite coatings showed enhanced conductivity, achieving a conductivity of 249.4 ± 11.2 S•cm −1 for a PEDOT content of 3.43 wt %. The characterizations based on atomic force microscopy (AFM), Raman spectroscopy, ultraviolet−visible (UV−vis) spectroscopy, and two-dimensional grazing-incidence small-angle X-ray scattering (2D GI-SAXS) confirmed that acid treatment induced conformational and crystalline changes of PEDOT that improved the film's conductivity. Furthermore, the electrochromic materials based on these composites possess a unique combination of electrochromic and photonic crystal properties, showing colors ranging from green, yellow, orange, and red in the PEDOT-bleached state to dark blue in the PEDOT-colored state under the voltage change from 0.8 to −0.6 V. The electrochromic composite demonstrated a high coloration efficiency (372.4 cm 2 •C −1 ), faster switching speed (2.4 s for coloring and 3.5 s for bleaching), and good cycling stability after the 20 000 s test. Moreover, the chiroptical property of the co-assembled CNC structure was maintained in switching. Our study indicates that these composites, mainly composed of natural materials, exhibit a unique combination of electrochromic and chiroptical properties, which makes them an environmentally benign electrochromic material with potential for use in smart windows, displays, chiral sensors, anticounterfeiting, and encryption.

Exploring the Core Parameters of CNC-Based Chiral Nematic Structures for Enhancing the Dissymmetry Factor of Right-Handed Circularly Polarized Luminescence

“…CNC suspensions were prepared through the sulfuric acid-mediated hydrolysis of Whatman ashless filter paper according to our previous work. , Briefly, 5 g of filter paper was cut into small pieces and hydrolyzed in 50 mL of 64 wt % sulfuric acids at 45 °C under vigorous stirring for 45 min. Then, the resulting faint yellow slurry was added into cold deionized water (10-fold of the acid solution) to stop the hydrolysis.…”

Dual‐band electrochromic materials for energy‐saving smart windows

“…Jin et al fabricated an EC photonic crystal coating by co-assembly of PEDOT:PSS and cellulose nanocrystals, further improving the electrical conductivity of the PEDOT:PSS through the H 2 SO 4 treatment. [50] The enhanced conductivity resulted in higher NIR optical modulation. Furthermore, the unique combination of EC and photonic crystal properties resulted in superior EC performance, including excellent high coloration efficiency (372.4 cm 2 •C −1 ), fast switching speed (colored/bleached time of 2.4 s/3.5 s), and good cycling stability after 20,000 s. In addition, more and more researchers have focused on assembling a PEDOT-based complementary structure IR ECDs, which can not only improve the EC performance but also enhance thermal regulation, showing great potential in smart windows and relative applications.…”

“…Jin et al fabricated an EC photonic crystal coating by co‐assembly of PEDOT:PSS and cellulose nanocrystals, further improving the electrical conductivity of the PEDOT:PSS through the H 2 SO 4 treatment. [ 50 ] The enhanced conductivity resulted in higher NIR optical modulation. Furthermore, the unique combination of EC and photonic crystal properties resulted in superior EC performance, including excellent high coloration efficiency (372.4 cm 2 ·C −1 ), fast switching speed (colored/bleached time of 2.4 s/3.5 s), and good cycling stability after 20,000 s.…”

Color-to-white switching electrochromic devices constructed by combining fused thienothiophene polymers and high-reflectivity electrolyte

“…Electrochromic devices (ECDs) can reversibly tune their optical properties via applying an external potential, presenting promising applications in smart windows, [1][2][3][4] military camouflage, [5][6][7][8] non-emissive displays, [9][10][11][12] etc., and have been attracting considerable academic and industrial attention. Generally, ECDs contain five layers, namely two conducting substrates, an electrochromic layer, an electrolyte layer, and an ion storage layer.…”