Solution-Processed Interfacial PEDOT:PSS Assembly into Porous Tungsten Molybdenum Oxide Nanocomposite Films for Electrochromic Applications

Electrochromic devices (ECDs) have received increased attention for applications including optoelectronics, smart windows, and low-emission displays. However, it has been recognized that the ECDs with transition-metal oxide (TMO) electrodes possess a high charge transport barrier because of their poor electrical conductivity, which limits their electrochromic performance. In this work, we addressed this limitation by utilizing a conjugated polymer to fabricate an organic–inorganic nanocomposite film that decreases the charge transport barrier of typical TMO electrodes. Using a conventional spray-layer-by-layer (spray-LbL) deposition technique, we demonstrate an electrochromic film composed of porous layers of tungsten molybdenum oxide (W_0.71Mo_0.29O₃) nanorods permeated with an interconnected conductive layer of poly­(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). The introduction of PEDOT:PSS is shown to significantly reduce the charge transport barrier, allowing the nanocomposite W_0.71Mo_0.29O₃/PEDOT:PSS electrode to exhibit significantly improved electrochromic switching kinetics compared with the deposited W_0.71Mo_0.29O₃ films. Furthermore, the optical contrast of the nanocomposite electrode was observed to be superior to both pure PEDOT:PSS and W_0.71Mo_0.29O₃ electrodes, with a performance that exceeded the linearly predicted contrast of combining the pure films by 23%. The enhanced performance of the PEDOT:PSS-intercalated porous W_0.71Mo_0.29O₃ nanocomposite electrodes and the facile synthesis through a spray-LbL method demonstrate a viable strategy for preparing fast assembling high-performance nanocomposite electrodes for a wide variety of electrochemical devices.