Haiming Lv

Novel morphology changes from 3D ordered macroporous structure to V2O5 nanofiber grassland and its application in electrochromism

Because vanadium pentoxide (V2O5) is the only oxide that shows both anodic and cathodic coloration electrochromism, the reversible lithium ion insertion/extraction processes in V2O5 lead to not only reversible optical parameter changes but also multicolor changes for esthetics. Because of the outstanding electrochemical properties of V2O5 nanofibers, they show great potential to enhance V2O5 electrochromism. However, the development and practical application of V2O5 nanofibers are still lacking, because traditional preparation approaches have several drawbacks, such as multiple processing steps, unsatisfactory electrical contact with the substrate, expensive equipment, and rigorous experimental conditions. Herein, we first report a novel and convenient strategy to prepare grass-like nanofiber-stacked V2O5 films by a simple annealing treatment of an amorphous, three-dimensionally ordered macroporous vanadia film. The V2O5 nanofiber grassland exhibits promising transmittance modulation, fast switching responses, and high color contrast because of the outstanding electrochemical properties of V2O5 nanofibers as well as the high Li-ion diffusion coefficients and good electrical contact with the substrate. Moreover, the morphology transformation mechanism is investigated in detail.

Near-infrared and Multicolor Electrochromic Device Based on Polyaniline Derivative

Electroactive conducting copolymers of aniline (ANI) and diphenylamine (DPA) are prepared on indium tin oxide (ITO) surface from 1 mol/L H2SO4 aqueous solution with different feed ratios of ANI to DPA by using a potentiostatic method. FTIR spectra and SEM measurements are used to confirm the formation of copolymers. Due to the combination of the N,N′-diphenyl benzidine and aniline units in the molecular chain, the copolymer films exhibit improved electrochemical and electrochromic properties, compared to PANI and PDPA. The copolymer [marked as P(ANI9-co-DPA1)] film prepared at a ratio of 9:1 (ANI/DPA) exhibits novel transmittance modulation both in visible and near-infrared (NIR) region between −0.8 V and 0.8 V (52% and 67% respectively) and fast response time (3.6 s for coloration and 2.3 s for bleaching at 600 nm). An electrochromic device (ECD) based on P(ANI9-co-DPA1) and PEDOT:PSS is also fabricated and shows a multicolor electrochromic performance, with a good optical contrast (29% in visible region and 40% in NIR region), acceptable response time (8.3 s for coloration and 7.5 s for bleaching at 600 nm) and long-term stability. Clear color changes from transparent (−0.8 V), bright green (0 V), seagreen (0.4 V) to dark slate gray (0.8 V) are demonstrated.

Improved Electrochromic Performance of Poly(3,4-ethylenedioxythiophene) by Incorporating a Three-Dimensionally Ordered Macroporous Structure

In this paper, three-dimensionally ordered macroporous (3DOM) poly(3,4-ethylenedioxythiophene) (PEDOT) films were electropolymerized from an ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim]PF6 ). The electrochromic performances of the 3DOM PEDOT films were studied. The 3DOM films exhibited high transmittance modulation (41.2 % at λ=580 nm), high ionic fast switching speeds (0.7 and 0.7 s for coloration and bleaching, respectively), and enhanced cycling stability relative to that exhibited by the dense PEDOT film. The relationship between the declining behavior of the transmittance modulation and the nanostructure of the film was investigated. A three-period decay process was proposed to understand the declining behavior. The 3D interconnected macroporous nanostructure is beneficial for fast ion and electron transportation, high ion accessibility, and maintenance of structure integrity, which result in enhanced cycling stability and fast switching speeds.