Fast, self-supplied, all-solid photoelectrochromic film

This paper describes the fabrication and the characterization of a new nanostructured and self-supplied photoelectrochromic device. The main properties of this film are its all-solid nature, its fast coloration time as well as its fast bleaching time. The photoelectrochromic film was manufactured by coating dye functionalized TiO2 nanoparticles (dye-TiO2) on a layer of WO3 nanoparticles. In order to improve their electrical conductance, both the dye-TiO2 and WO3 layers were properly doped with single wall carbon nanotubes (SWNT) bearing COOH groups. A layer of PEDOT/PSS was cast between the dye-TiO2 layer and the ITO counter electrode, without the use of any fluid component. When exposed to the light, SWNT doped dye-TiO2 layer generates electrons that reduce the WO3 layer. As a consequence of this redox reaction, the film changes its color if the two external electrodes are not short-circuited. On the contrary, a fast bleaching of the device can be achieved by shortcircuiting the electrodes.