DEVELOPMENT OF WAVELENGTH-SELECTIVE SHUTTERS FOR DEVICE APPLICATION FOR FILTERS AND SMART WINDOWS

Ideal wavelength selective shutters (or filters) need to have sharp, h igh intensity, easily switchable absorption bands in the desired regio n of the electromagnetic spectrum. If such devices are to be used for smart window applications, then selective control of all the visible a nd near infra-red regions of the electromagnetic spectrum would be des irable. No single material, as yet, offers such selectivity. The choic e and properties of such material would also depend on ease of use and friendliness to the environment. Metal phthalocyanine materials are u seful electrochromics, the neutral molecules are nontoxic, brightly co loured (have narrow absorption bands with high extinction coefficients ) and are also stable to heat and light. Metal bisphthalocyanine elect rochromics (where the metal is based on the rare earth elements, Zr, S n or Pb) have some promise in this area and are discussed. A number of metal monophthalocyanines, compounds where the metals are transition elements (such as V, Cr, Mn, Fe and Co) and nontransition elements (su ch as Al, Si and Sn) that offer some useful spectral properties, are a lso discussed. The possibilities of using 'cocktails' of these compoun ds to give desirable performance, their projected advantages and disad vantages are also debated. A bright future is envisaged for these mate rials.