Solution processable neutral state colourless electrochromic devices: effect of the layer thickness on the electrochromic performance

In this study, a neutral state colourless electrochromic device fabricated through a solution process is introduced. The device contains indium doped transparent oxide coated glass as the transparent conductive electrode, poly(N-(2-ethylhexyl)carbazol-3,6-diyl) (PCbz) as the anodically colouring material, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the ion storage layer and a lithium perchlorate based conducting gel electrolyte. A maximum optical contrast (ΔT%) of 58% at 800 nm is achieved by optimizing the film thickness of both the organic layers. The device that has layers of 220 nm PCbz and 120 nm PEDOT:PSS thickness revealed a high coloration efficiency (1246 cm2 C−1) and colouring and bleaching response times of 5.6 s and 2.3 s, respectively.