A novel high-contrast ratio electrochromic material from spiro[cyclododecane-1,9'-fluorene]bicarbazole

A novel electroactive spirocyclododecylfluorene monomer named 2,7-bis(carbazol-9-yl)-9,9'-spiro[cyclododecane-1,9'-fluorene] (SFC) was synthesized and electrochemically polymerized to give a very stable multi-electrochromic polymer (poly-SFC). Two separate oxidation processes were observed for both SFC monomer and poly-SFC that carries two carbazole units. The polymeric film of poly-SFC was coated onto ITO/glass surface, and it shows different colors (transparent, yellowish green, green, and dark green) upon stepwise oxidations. An electrochromic device based on poly-SFC was assembled in the sandwich cell configuration of ITO/poly-SFC//gel electrolyte//PEDOT/ITO. Poly-SFC exhibits 90% of transparency at neutral state and a high contrast ratio (ÎT = 58% at 800 nm). This device constructed from it represents a response time of about 1 s, high coloration efficiency (1377 cm2 C-1) and retained its performance by 96.4% even after 1000 cycles. Exhibiting high transparency at neutral state, reversible redox behavior, resistance to overoxidation, and especially high contrast ratio at near IR region can make poly-SFC be useful and promising candidate for electrochromic applications despite having a relatively slow response time. © 2010 Wiley Periodicals, Inc