High-performance electrofluorochromic devices based on aromatic polyamides with AIE-active tetraphenylethene and electro-active triphenylamine moieties

Abstract

Novel electrochromic (EC) and aggregation-enhanced emission (AEE)-active triphenylamine (TPA)-based polyamides were prepared with 4-cyanotriphenylamine (TPA-CN), 4-methoxytriphenylamine (TPA-OMe), cyclohexane (CH) and tetraphenylethene (TPE) moieties via condensation polymerization. The emission from the polyamides could be quenched from the neutral to oxidized states effectively due to the structural planarization and optical absorption shift of TPA units during electrochemical switching. With the introduction of n-heptyl viologen (HV) into the device system as a counter EC layer for balancing charges, the resulting high-performance electrofluorochromic (EFC) devices based on TPA-CN-CH as a photoluminescent (with a fluorescence quantum yield of up to 46% in the film state) and redox-active layer showed a high fluorescence contrast ratio (I_off/I_on) of 105. The HV-containing TPA-OMe-TPE-based EFC device displayed the shortest response time of less than 4.9 s, and excellent improvement in reducing the switching recovery time and lowering the oxidation potential could also be achieved. Thus, judiciously designed multi-functional polymers with both redox- and AEE-active features are a crucial and feasible approach for preparing highly efficient EFC devices.