Advances in electrochromic materials

The development of a Microsoft® Excel® spreadsheet is described, for the accurate calculation of CIE (Commission Internationale de l’Eclairage) 1931 xy chromaticity coordinates and luminance data from visible region absorption spectra recorded in transmission mode. Using firmly established CIE principles, absorbance-wavelength data from visible spectra are taken as input, with chromaticity coordinates being generated as output. Colour stimulus measurement example calculation results are firstly presented for aqueous solutions of the dyes, Erythrosin B (red, x, y = 0.608, 0.365), Acid Green 25 (x, y = 0.086, 0.298) and Remaxol Brilliant Blue R (x, y = 0.153, 0.045), and then for tracking electrochromic in situ colour stimulus changes in the methyl viologen and di-n-heptyl viologen systems. The quantification of colour during each viologen dication to cationradical reduction process, and each reverse (oxidation) process, showed that subtle changes in both hue and luminance could be detected, with evidence of colour contributions from both the cation radical and the cation radical dimer. Ruthenium purple (RP) films on transmissive tin-doped indium oxide (ITO)/glass substrates have been synthesised by a novel electrochemical coagulation technique. Using the CIE system of colorimetry, the colour stimulus of the electrochromic RP films and the changes that take place on reversibly switching to the colourless form have been calculated from in situ visible spectra recorded under electrochemical control. (Continues...).