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.