High contrast asymmetric solid state electrochromic devices based on layer-by-layer deposition of polyaniline and poly(aniline sulfonic acid)

Layer-by-layer (LbL) self-assembly was employed for alternating deposition of two electrochromic polymers to fabricate a single film composite. We report a wide spectral range, high contrast asymmetric solid state electrochromic device, fabricated by LbL assembly of the polycation polyaniline (emeraldine base) (PANI) and the polyanion poly(aniline sulfonic acid), (PASA). Detailed spectral and electrochemical investigation of the dual electrochrome thin film confirm that both electrochromic polymers contribute to the electrochromic and electrochemical characteristics of the composite. Under the application of +/-2.3 V potential the system exhibited an average contrast of 49.7% across the full visible spectrum. The dual electrochrome system was compared to single electrochrome systems, and it was observed that PANI predominantly affects the electrochromic optical spectra of the composite, whereas PASA increases the switching speed. (C) 2010 Elsevier Ltd. All rights reserved.