Synthesis and multicolored electrochromism of polycarbazoles containing oxadiazole

Abstract

A carbazole derivative (COP) containing (trifluoromethyl)pyridine and oxadiazole and a carbazole derivative (COI) containing isoxazole and oxadiazole are synthesized, and their corresponding polymers (P(COP) and P(COI)) are electrosynthesized on a transparent conductive indium tin oxide glass surface using potentiostatic techniques. The P(COP) and P(COI) films exhibit reversible electrochemical and spectrochemical behaviors from the neutral-to-oxidized and oxidized-to-neutral states. The P(COP) is yellow ocher, grayish-green, and khaki green at 0.0, 1.4, and 1.5 V, respectively, whereas P(COI) is light grayish-green, light greenish-yellow, and light green at 0.2, 1.2, and 1.4 V, respectively, in solutions. The P(COP) demonstrates a transmittance change (ΔT = 40.1% at 1100 nm) and an adequate coloration efficiency (η = 162.1 cm2 C−1 at 1100 nm). Dual-layer polymeric electrochromic devices (ECDs) are fabricated using polycarbazoles containing oxadiazole and poly(3,4-propylenedioxythiophene) (PProD) as the anodic and cathodic layers, respectively. The P(COI)/PProDBz2 ECD displayed four color transitions (light bluish-gray, bluish-gray, xenon blue, and indigo) from the bleached to the colored state. Moreover, the P(COP)/PProDBz2 ECD displays a considerable ΔT (48.0% at 624 nm), and the P(COI)/PProDBz2 ECD displays a substantial coloration efficiency (η = 530.6 cm2 C−1 at 623 nm). In addition, polycarbazoles containing oxadiazole/PProD ECDs demonstrate high electrochemical redox stability and a short bleaching and coloring time. These findings indicate that polycarbazoles containing oxadiazole are promising electrochromic materials and can be used in multicolored and energy-saving ECDs.