Investigation of P3HT:WO3 hybrid electrochromic thin films prepared by solution blending doping

Although poly(3-hexylthiophene) (P3HT) is a promising p-type conjugating polymer to optimize optical and electrical properties, it is known to be chemically unstable. To overcome this unstability, WO3 incorporated P3HT hybrid thin films has been synthesized by very simple solution blending doping method. Different amounts of WO3 were added into the P3HT solution and the incorporation of WO3 particles was confirmed by scanning electron microscopy, atomic force microscopy, and photoluminescence spectroscopy. The electrochemical reactions in 1 M lithium perchlorate (LiClO4)/propylene carbonate (PC) were studied by cyclic voltammetry and by electrochemical impedance spectroscopy. With the increase amount of WO3 in P3HT, the electrochromic efficiency increases first and then decreases. The optimum concentration was found as 30 wt% of WO3. The efficient interaction and well distribution between WO3 and P3HT improves the capacitive properties and electrochromic performance resulting a 110% increase in coloration efficiency (from 220 cm2/C to 464 cm2/C). Moreover, WO3 doped hybrid films shows long-term cyclability than undoped P3HT films. Structural and electrochemical investigations suggest that the optimum amount of WO3 doping is an alternative way to obtain high performance and environmentally stable electrochromic devices.