Described herin are molecules for use in organic light emitting diodes. Example molecules comprise at least one acceptor moiety A, at least one donor moiety D, and optionally one or more bridge moieties B. Each moiety A is covalently attached to either the moiety B or the moeity D, each moiety D is covalently attached to either the moeity B or the moeity A, and each B is covalently attached to at least one moiety A and at least one moiety D. Values and preferred values of moieties A, D and B are defined herein.
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.