Design and synthesis of multi-coloured electrochromic and electrofluorochromic asymmetric materials by adjusting the central potential of the compounds

Abstract

Carbazole and triphenylamine derivatives have become popular research topics in the field of electrochromism and electrofluorochromic due to their excellent reversible oxidative activity, reversible colour change and reversible fluorescence change during electrochemical processes. Four asymmetric carbazole-triphenylamine derivatives 6a-d were designed and synthesized. Both ultraviolet absorption (UV) spectra and fluorescence emission (PL) spectra changed with the change in voltage applied to all compounds. These compounds were fabricated into electrochromic and electrofluorochromic devices, and these devices exhibited excellent cycling stability (cycling stability remains above 95% after 11000 s), short switching time (1.1 s ∼ 1.6 s), high PL contrast (146 ∼ 172), and high colour contrast (47.2% ∼ 50.6%). All the samples fluoresced off in the oxidised state and exhibited alternating yellow-green characteristics, and fluoresced on in the reduced state while exhibiting a highly transparent and colourless state. The experimental results indicated that these materials are expected to be used for the preparation of wearable devices and transparent displays. The research demonstrated that rich color changes can be achieved by adjusting the electrochemical properties of dual redox centered materials.