THE EFFECT OF FERROCYANIDE ON THE PERFORMANCE OF HEPTYL VIOLOGEN-BASED ELECTROCHROMIC DISPLAY DEVICES

The write-erase efficiency of electrochromic cells incorporating hepty l viologen (HV) is decreased if di-reduced HV0 is formed: this is obse rved as a failure to electro-oxidise the colour of the display. This f ailure is caused by comproportionation of electrogenerated HV0 with HV 2+ (from the solution bulk); comproportionation results in the generat ion of electrochemically inert radical-cation dimer HV22+. Addition of ferrocyanide to the solution as an electron mediator improves the wri te-erase efficiency of an HV-based device by promoting a different com proportionation mechanism that does not involve the radical-cation dim er. (C) 1997 Elsevier Science S.A.