Multi‐Amino Triarylamines for Electrochromic and Electrofluorochromic Applications with Exceptional Stability and Extraordinary Fluorescence Modulation

This study investigates arylamine small molecules functionalized with multiple primary amino groups and various extended π bridges (TPPA-2N, TPPA-4N, and TPB-4N) to evaluate their opto-electrochemical behaviors. TPPA-4N exhibits polyelectrochromic features and outstanding stability during continuous cyclic voltammetry scans, maintaining 99.0% reversibility after 15 000 cycles and 95.2% reversibility after 10 000 cycles at the first and second oxidation states, respectively. After being fabricated into devices, the TPPA-4N/HV device retains 96% stability after 1000 switching cycles at the first oxidation state and 500 cycles at the second oxidation state, respectively. In addition, the TPPA-4N/HV device also exhibits a blue emission at the neutral state with an exceptional intensity contrast ratio (ICR) of up to 950-fold for electrofluorochromic (EFC) applications, resulting from well-controlled absorption-emission modulation that causes the self-absorption effect. Additionally, the TPB-4N/HV device reveals a moderate ICR of 393-fold. By blending TPPA-4N and TPB-4N, the resulting EFC device exhibits a highly reversible two-stage EFC behavior, transitioning from lime to olive green emission and then completely quenching with gratifying ICR values at each emitting color.