By combining an electronically conductive polymer, a solid state polymer electrolyte and a metal oxide (vanadium oxide), a solid state electrochemical cell was constructed. The optical absorption of the cell could easily be changed by changing the applied cell potential. The polymeric materials used have the advantage of very easy fabrication of thin films: spin-coating or solution-casting for poly(3-octylthiophene) and template polymerization for polypyrrole. Owing to the difference in coulombic capacity and coloration efficiency between the metal oxide and the conjugated polymer, the optical changes of the cell are mainly due to optical changes of the polymer. Thus, this technique can also be used for studying the doping process of the polymer and the stability of the states induced by doping.

We have intercalated c-axis oriented Y1Ba2Cu3O7−δ thin films with Li+ ions. Undoped films were grown by a pulsed laser deposition technique. A strong correlation was observed between the superconducting properties of Y1Ba2Cu3O7−δ and the number of inserted Li+ ions. A maximum Tc of 92.5 K was measured for intercalation with one Li+ ion per unit cell.

Electrochromic tungsten oxyfluoride thin films were made by reactive magnetron sputtering of W in Ar+O2+CF4. A moderate CF4 fraction led to deposition at enhanced rates and films with fairly neutral color in their dark state. Transparent vanadium oxyfluoride films were made analogously; they were annealing post-treated in Ar+O2+CF4. By fluorination it was possible to avoid the short-wavelength absorption that otherwise limits the usefulness of V2O5 in electrochromic smart windows. A transparent, adhesive, viscoelastic polymer electrolyte laminate was developed. It has good voltammetric cycling capability (106 times), good optical transmittance, and high conductivity, ranging from 10-6 S/cm (-10 degree(s)C) to 10-3 S/cm (80 degree(s)C).

By combining a processable electronically conductive polymer [poly(3-octylthiophene) (P3OT), polypyrrole (PPy)], a solid polymer electrolyte [(PEO)8LiClO4], and a metal oxide (V2O5), a solid state electrochromic device is constructed. The polymer films are fabricated by spin coating from solution (P3OT) and template polymerization (PPy). The metal oxide is electrochemically doped with Li+ and the electrodes are mounted in a sandwich structure with a thin film of polymer electrolyte in between. As the applied cell potential is changed, the optical absorption of the cell is changed. Owing to the difference in columbic capacity between the different materials, the optical changes of the cell are due to optical changes of the polymer only. This means that, instead of having to adapt often contradictory optical changes in two electrochromic materials for the desired application, one can use a polymer with a proper optical signature, letting the band gap determine the electro-optical behavior of the cell.

Films of NiOxHy were made by reactive dc magnetron sputtering of Ni followed by electrochemical treatment in KOH. Infrared reflectance spectroscopy with obliquely incident p-polarized light documented a unique topochemical reaction with the bleached state being β–Ni(OH)2 and the colored state being β–NiOOH. The same technique yielded clear, though not yet fully understood, data on the evolution of electrochromism during potentiodynamic cycling.

Thin films of LiyV2O5 (00.5 μm there are absorption peaks associated with V4+ ions both for p-X and n-X materials, and a broad absorption feature for p-X Liy V2O5 that is tentatively ascribed to electron hopping in the crystallographic b direction. The absorption goes up for increased y, as expected from the higher V4+ density.

LiyV2O5 films were produced by reactive de magnetron sputtering followed by electrochemical posttreatment in LiClO4. X-ray diffraction showed an orthorhombic structure. Spectrophotometric transmittance and reflectance measurements demonstrated that the luminous and solar absorptance increased moderately when y increased from zero to unity. It is argued that LiyV2O5 is useful as an ion storage material operating in conjunction with electrochromic films.

Nonstoichiometric nickel oxide films were made by reactive dc magnetron sputtering. Subsequent electrochemical treatment in KOH established electrochromism. The material was studied by combined mechanical and optical measurements during electrochemical cycling, spectral infrared reflectance, XPS, and X-ray diffraction. Mechanical stress data showed that electrochromic bleaching was associated with proton insertion. P-polarized infrared reflectance showed OH stretching vibrations representative of "free" OH for the bleached state and OH in the presence of hydrogen bonds for the coloured state. XPS data for 01 s core level electrons indicated one binding state in the bleached material and two binding states in the coloured material. Heat-treated samples had significantly decreased electrochromism.

We introduce a laminate two-layer approach to electrochromic smart windows. It incorporates two glass panes, each having a two-layer coating, laminated by a transparent adhesive solid polymer electrolyte. Each coating has a transparent conducting base layer (In(2)O(3):S(n)) and a top layer of an ion-insertion compound (based on WO(3) or V(2)O(5)). The layers were made by evaporation or sputtering. Cyclic voltammetry in liquid electrolytes and spectrophotometry were used to characterize the layers. A novel electrolyte was developed: it comprised a methyl methacrylate network incorporating poly(propylene glycol) complexed with lithium perchlorate. Initial optical data are reported for laminated devices having an active electrochromic Li(x)WO(3) layer and a passive Li(y)V(2)O(5) counter electrode.

We introduce a laminate two-layer approach to electrochromic smart windows. It incorporates two glass panes, each having a two-layer coating, laminated by a transparent adhesive solid polymer electrolyte. Each coating has a transparent conducting base layer and a top layer of an ion insertion compound. We made ion-insertion layers of W03, V205 and NiOx by sputtering and evaporation. These layers were characterized by cyclic voltammetry in liquid electrolytes and by spectrophotometry. Our novel electrolyte comprised a methyl methacrylate network incorporating poly (propylene glycol) complexed with lithium perchlorate. Initial optical data are reported for laminated devices having an "active" electrochromic LixWO3 layer and a "passive" LixV205 counter electrode.

Electrochromic materials are characterized by reversible but persistent changes of the optical properties when subjected to suitable electrochemical reactions. Electrochromism can be utilized in windows, most conveniently by exploiting all-solid-state multilayer coating backed by glass. The multilayer coating should comprise the following sequence of layers: a transparent and electrically conducting base layer, an electrochromic layer, and electrolyte, a conterelectrode, and a transparent conducting top layer. For window applications, the electrolyte should be transparent, and the conterelectrode must be either optically passive (colorless irrespective of its ionic content) or electrochromic in a sense that is complementary to the electrochromism of the electrochromic layer. The latter condition implies that if the electrochromic layer is cathodic (anodic), the counterelectrode must be anodic (cathodic). This paper reports preliminary data taken on samples with electrochromic layers based on tungsten oxide, WO{sub 3}, and nickel oxide, NiO, and an intermediate solid electrolyte of poly(ethylene oxide) doped with lithium perchlorate, (PEO){sub 8}LiClO{sub 4}, where 8 signifies the number of oxygen heteroatoms per lithium ion.

NiOx films were made by dc magnetron sputtering of Ni in O2 at a rate of <0.15 nm s−1. The grain size was ∼10 nm and the crystal structure was cubic. Electrochemical hydration, and ensuing conversion to electrochromic NiOxHy, took place in KOH. Spectrophotometric measurements in the 0.35–2.5-μm range showed that it took >100 color-bleach cycles to establish a fully bleached state. When removed from the KOH electrolyte, a colored NiOxHy film increased its transmittance by <1% per h. The luminous and solar transmittance could be varied between 80% and 20% and between 74% and 29%, respectively.

We study thermochromism in fiber composites with a view to their possible use for controlling the transmission of luminous and solar radiation. Spectrophotometric measurements of collimated and total transmittance were carried out for quartz fibers in carbon tetrachloride. The collimated transmittance showed a peak structure consistent with index matching. The total transmittance was almost featureless; the integrated luminous and solar transmittance decreased by ~20% as the temperature went from 0 to 35 degrees C if the fiber fraction was ?5 vol %. The optical properties could be reconciled with a four-flux model with parameters obtainable from the Mie theory. Specifically, we treated scattering off cylindrical objects in the Rayleigh- Gans limit.

This paper outlines some recent work on electrochromic and thermochromic coatings for smart windows. The purpose is to illustrate materials options and operation principles rather than to present detailed results. Specifically, we discuss electrochromic NiOxHy films operated in a KOH electrolyte, electrochromic LixWO3 films operated in conjunction with a novel transparent elastomer electrolyte, thermochromic V02 films whose semiconductor-metal transition point was depressed as a result of a dielectric top layer or by applied strain, and a thermochromic material comprising Si02 fibres in CC14.