In‐situ preparation and electrochromic properties of TiO₂/PTPA‐HTAN core‐shell nanocomposite film

Abstract

A new star-shaped structure conjugated microporous polymers, poly (2,8,14-tri [4-diphenyl-benzene]-hexaazatrinaphthylene) (PTPA-HATN), was designed and in-situ electrochemically polymerized on the surfaces of FTO electrodes with a directional alignment TiO 2 nanorod array to obtain TiO 2 /PTPA-HATN coreshell nanocomposite films. Compared with the PTPA-HATN film, the TiO 2 / PTPA-HATN composite film exhibits higher optical contrast and faster response time, with contrast of 57% at 783 nm, coloring time of 3.62 s and discoloring time of 2.55 s (43%, 4.63 s and 4.77 s for PTPA-HATN film, respectively). After 400 cycles, the contrast of nanocomposite film decreased by 28%, while the PTPA-HATN film basically lost its electrochromic properties. A simple threelayer EC prototype device based on TiO 2 /PTPA-HATN nanocomposite film constructed with hydrogel electrolyte clearly shows color changes at different voltages. On the one hand, the formation of core-shell porous nanostructure of TiO 2 /PTPA-HATN composite film provides a larger ion doping/de-doping interface, shortening the average diffusion length of ions. On the other hand, the large indented polymer-nanorods contact interface makes it difficult for the polymer to detach from the electrode, thus significantly improving the cyclic stability of the composite film. K E Y W O R D Score-shell nanocomposite film, electrochemical polymerization, electrochromic, poly (2,8,14-tri[4-diphenyl-benzene]-hexaazatrinaphthylene), TiO 2 nanorod arrays | INTRODUCTIONElectrochromic materials have attracted more and more attention in recent years due to their color switchable, low power consumption driven, tunable optical properties and so on, which makes them become candidates for display, smart window and energy-saving technologies. [1][2][3] The polymer electrochromic (PEC) materials are one of the research hotspots at present because of their advantages of easy tailoring of their molecular structure, wide range of color change, high-optical contrast, fast switching time, and excellent processability and so forth. [4][5][6][7][8] At present, the rich color display properties of PEC materials can be realized by molecular structure design or modification, such as donoracceptor (D-A) structure design, introduction of functional groups and copolymerization of different monomers. 9-13 However, fast switching time and long-term cycle stability, for commercial applications, are also indispensable