Enhanced electrochromic performance of WO3/PEDOT by π-electron conjugation system

Tungsten oxide (WO3) is one of the most extensively studied electrochromic materials and regarded as a promising candidate for commercial application. However, its slow response time and poor coloring efficiency limit its practical applications. Here, tungsten oxide and poly(3,4-ethyldioxythiophene) (PEDOT) hybrid nanorod array are prepared by hydrothermal method and in situ electro-polymerization. The WO3/PEDOT hybrid nanorod array exhibits shorter response time (22.4 s coloring and 26.0 s bleaching) compared to WO3 film (27.2 s coloring and 30.0 s bleaching) and a rapid Li+ diffusion rate (3.65 × 10−12 cm2/s). Within the range of λ = 700 nm, the optical contrast of the composite film increases from 42.8 % (WO3) to 68.2 % (WO3/PEDOT). The coloring efficiency and stability of WO3/PEDOT composite film are also improved compared to individual components (WO3 or PEDOT). The improvement of the electrochromic performance can be attributed to the highly ordered nanorod structure of WO3/PEDOT composite film which provides a larger surface area and a faster charge transport path. The special 1D structure of the nanorod can also increase the length of the PEDOT conjugate chain, which in turn facilitate the π-electrons transfer and accelerate the rate of electron and ion transfer, resulting in the decrease of the response time. The novel structure of WO3/PEDOT combines the best advantages of WO3 and PEDOT, making it an ideal electrochromic material.