An electrochromic device (10) incorporates a reversibly colour-changing organic polymer film (20) as part of the display electrode. The display polymer film (20) is capable of undergoing reversible oxidation and/or reduction to a charged, coloured, conductive state. Upon reversing the charge, the polymer returns to its virgin colour. The display films are comprised of linear fused heterocyclic ring systems, optionally with connecting units, or linear monocyclic ring systems and connecting units. The device requires low currents to operate and switch from the virgin state to the coloured state. It also can optionally be operated to exhibit several colours.
A rechargeable metal ion cell comprising: an anode comprising at least one metal; a charge-carrying electrolyte comprising a charge carrying medium and at least one metal salt; and an organic polymer cathode, wherein such cathode comprises at least one N-substituted polyphenothiazine polymer [polymer (P)], such polymer (P) comprising at least one N-substituted phenothiazine recurring unit of formula:
wherein R′ is an electron-withdrawing group comprising at least one heteroatom selected from the group consisting of O, S, P, and N.