含普魯士藍薄膜式及混合式之電致色變元件

Abstract

In this thesis, a novel process for the preparation of Prussian blue (PB) electrode was presented with the electro-optical properties of the PB film. Also, an optimization work of a complementary thin-film-type device composed of PB, poly (3, 4-ethylenedioxythiophene) (PEDOT), and ionomeric poly(vinyl butyral) (PVB) and a complementary hybrid-type device composed of PB, heptyl violoten (HV), and succinonitrile were studied. A novel process is developed for the preparation of Prussian PB film, involving its electrodeposition from its precursor solution, containing additionally the surfactant, cetyltrimethylammonium bromide (CTAB); the film is denoted as CTAB-modified PB film. The present approach allows for mitigating the energy barrier of redox reactions between Prussian blue and its reduced state, Everitt’s salt. The absorbance spectra of the CTAB-modified PB exhibit a maximal optical difference at 690 nm. The transmittance changes (ΔT) of CTAB-modified PB film and unmodified PB film were measured in the electrolyte of 0.5 M KCl and 0.01 M HCl at 690 nm. It reveals that CTAB-PB film took 4.2 s and 2.4 s for darkening (oxidation) and bleaching (reduction), respectively, for 44.2% transmittance change (ΔT), whereas the unmodified film required 35 s and 55 s for 42.1% of ΔT. By an electrochemical quartz crystal microbalance (EQCM) analysis, it is observed that the insertion and extraction of potassium ions and water molecules at the interface of the CTAB-modified PB film and the electrolyte solution are faster than those of the unmodified PB film. It result from the less charge transfer resistance of the CTAB-modified PB film than that of the unmodified film. Also, during the potential-cycling of the CTAB-modified PB film, it was found to be stable, with reference to the stability of the unmodified PB film. An ionomeric PVB electrolyte was employed for a complementary thin-film-type electrochromic device. The anodically coloring material and the cathodically coloring material of the device are PB and PEDOT, respectively. Both electrodes were characterized in LiClO4 propylene carbonate (PC) solution individually. The ionic conductivity of ionomeric PVB electrolyte can reach 9.9×10-4 S/cm. With sandwiched the PVB electrolyte between PB electrolyte and PEDOT electrode, the device has optimal absorbance change at 620 nm on the equilibrium spectrum. It provides 39.8% transmittance change (ΔT) at 620 nm by switching at the range between 1.0 and -1.1 V (PEDOT vs. PB) with a bleaching time of 1.2 s and a darkening time of 1.5 s. The coloration efficiency at 620 nm of the device was calculated to be 270.8 cm2/C. The device performs 37.28 % of optical contrast at 690 nm for the first cycle, be activated after 5 cycles. Experiencing 15,000-cycle operation, the transmittance change is only 32.1% left. Another complementary electrochromic device which was hybrid type and all-solid-state was also assembled. Composed of PB and HV, it had the supporting electrolyte in succinonitrile matrix. By applying different potential bias, the device could exhibit various color intensities. The maximal transmittance change was located at 610 nm. Operated from 0.0 V to -1.8 V, the device showed its transmittance from 76.97 to 4.30% at 610 nm, with a transmittance change of 72.67%. The effects of operation conditions, the darkening voltages, and the bleaching voltages on the response time were also observed. Moreover, the device, operating between 0.0 and -1.6 V, remained 67.57% of transmittance change after 50,000 cycles.