Five-layer-structured electrochromic glass (window), containing a transparent conductive layer, an electrochromic layer, an ionic conductive layer, an ionic storage layer and a second conductive transparent layer, was fabricated. The electrochromic glass adopts the conjugated polymer, poly[3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine] (PProDOT-Me2), as a blue electrochromic active layer, vanadium pentaoxide film as an ion storage layer and polymer gel electrolyte as the ionic transport layer. Dimension of smart glass up to 12 x 20 inch was developed. UV curable sealant was applied for the sealing devices. Color changing or switching speed of 12 x 20 inch smart glass from dark state to the transparent state (or vise versa) is less than 15 seconds under applied 1.5 voltages. Besides the long open circuit memory (the colored state or transparent state remains the same state after the power is off), the smart window can be adjusted easily into the intermediate state between the dark state and the transparent state by just simply turn the power on or off. No space consuming or dirt collecting shades, curtains or blinds are needed. The applications of the smart window, e.g. in the aircrafts, automobiles and architectures were discussed as well.
A preparation and characterization of thin film vanadium oxide for use as a transparent ion storage layer/counter-electrode in organic ECDs is reported. A cathodic polymer film, Poly[3,3-dimethyle-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine] (PProDOT-Me<sub>2</sub>) was used as the electrochromic material. Counter-electrodes were prepared using a sol-gel method and deposited using electrophoresis. Indium Tin oxide (I TO) glass was used as an electrically conductive and transparent substrate. This paper focuses on optimized characteristics complimentary to a PProDOT-Me<sub>2</sub> based electrochromic thin film. Gels of vanadium oxide were created from V<sub>2</sub>O<sub>5</sub> powder mixed with hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) and deionized water. Thin films were deposited onto a substrate submerged in the solution and subjected to cyclic voltammetry. Deposition parameters were varied and their effect on counter electrode characteristics investigated. The thin film exhibited a capacitance curve similar to the PProDOT-Me<sub>2</sub> based EC film while maintaining a transmittance greater than 60% indicating that V<sub>2</sub>O<sub>5</sub> is a suitable material. The ensuing 1 inch x 1 inch smart window exhibits a change in transmittance of 60% and a lifetime of over 100,000 cycles at a switching speed of 1 second. Larger sized devices of six and twelve inches were successfully prepared and switched between the dark blue and transparent states in less than 15 seconds.
The preparation and characterization of a type of ECD which was based on a cathodic EC polymer film, Poly [3, 3-dimethyl-3, 4-dihydro-2H-thieno [3, 4-b][1, 4] dioxepine] (PProDOT-Me<sub>2</sub>) is reported. A typical device was constructed by sandwiching a gel electrolyte between a PProDOT-Me<sub>2</sub> EC film deposited on Indium Tin oxide (ITO) coated glass and a counter electrode which was also ITO glass coated by a Vanadium oxide (V<sub>2</sub>O<sub>5</sub>) thin film. The ECD has been characterized. Device contrast ratio, measured as Ε%<i>T</i>, was equal to 60%, and ranged from 2% to 62% between the colored and bleached state measured at 580 nm. A lifetime of over 100,000 cycles between the fully oxidized and fully reduced state has been achieved with only 6% change in the transmittance. The switching speed of a 2.5cm x 2.5cm ECD could be reached in 1 second between the bleached and colored state. The device also has a long open circuit memory. It can remain in the bleached or colored state without being energized for 30 days, and the change in transmittance is less than 6% in colored state. The cyclic voltammetry method was used to detect the moisture content in the gel electrolyte. ECDs of various dimensions were also prepared, 2.5cm x 2.5cm, 7.5cm x 7.5cm, 15cm x 15cm and 30cm x 30cm. The largest scale EC polymer device achieved is 30cm x 30cm. Low sheet resistance ITO glass and a thin-film silver deposition frame were applied to overcome the electric potential drop across the ITO glass surface.
A comparison of key parameters of seven different gel electrolytes for use in electrochromic devices (ECD) is reported. The ionic conductivity, transmittance, and stability of the gel electrolytes are important considerations for smart window applications. The gel electrolytes were prepared by combining polymethylmethacrylate (PMMA) with a salt and a solvent combination. Two different salts, lithium perchlorate (LiClO4) and trifluorosulfonimide (LiN(CF3SO2)2), and three solvent combinations, acetonitrile and propylene carbonate (ACN and PC), ethylene carbonate and propylene carbonate (EC and PC), and Gamma-butyrolactone and propylene carbonate (GBL and PC) were investigated. Results show that gel electrolytes composed of a LiClO4 and GBL+PC combination and a LiClO4 and EC+PC combination are the best candidates for a smart window device based on its high conductivity over time and various temperatures, as well as its electrochemical stability and high transmittance.
The synthesis, characterization and polymerization of two new electrochromic (EC) monomers based on 3, 4-alkylenedioxythiophene are reported. One is 3, 4-bis-(2, 2, 2-trifluoro-ethoxy)-thiophene which contains electron withdrawing group. Another is 6, 6-dimethy-6, 7-dihydro-5H-4, 8-dioxa-2-thia-6-sila-azulene which contains an electron donating group. Primary experiment results show that the new monomers have potential to form EC materials with new colors after polymerization. Color mixing of two EC polymers with blue and red color was studied. The principle of subtractive color mixing for achieving new color EC materials is also demonstrated.
A large contrast ratio and rapid switching EC polymer device which consists of a laminated two-layer structure between two electrodes was prepared. The new design consists of an ITO glass electrode, a cathodic EC polymer film, a gel electrolyte and a counter-electrode that replaces the anodic EC polymer and ITO electrode. Several types of EC polymers, such as, poly[3,3-dimethyl-3,4-dihydro-2H-thieno(3,4-b)(1,4)dioxepine] (PProDOT-(CH<sub>3</sub>)<sub>2</sub>) and
poly[3,4-(2,2-dimethylpropylenedioxy)-pyrrole] (PProDOP-(CH<sub>3</sub>)<sub>2</sub>) were synthesized as cathodic EC polymers. A carbon-based counter-electrode was prepared for comparison with an Au-based counter-electrode. Screen-printing was utilized for the carbon-based counter-electrode. Lithography and sputtering were used for the Au patterned glass counter-electrodes. Several kinds of polymer gel electrolytes were prepared for solid-state applications. Color change of high contrast ratio of visible light transmittance (>ΔΤ55%)of the device is rapidly obtained (0.5-1s) when even less than 2.5V is applied. The repeatability of color changeable EC polymer windows was estimated by the method of electrochemistry and spectrophotometry. This "smart window" technology can be used in many applications where a rapid
color change between transparent and color states is required.
Recent development of dendron-containing NLO chromophores and polymers is summarized. By modifying the chromophore shape or applying the site isolation principle to these materials, we have systematically build up our understanding of how to molecular engineer the NLO materials. In this process, we have introduced the dentritic structures to these materials, varied from 3-D shaped dendritic chromophore, to fully-functionalized dendrimers with the center cores of NLO chromophores and crosslinkable periphery, and to side-chain dendronized NLO polymers. Compared to the conventional designed organic NLO materials, these nanoscale tailored NLO chromophores and macromolecules provide great opportunities for the simultaneous optimization of macroscopic electro-optic activity, thermal stability, and optical loss.