Transmissive to Dark Electrochromic and Fluorescent Device Based on Poly(fluorene-bisthiophene) Derivative

Films of a poly(fluorene-bisthiophene) derivative, named PFBT, were electrodeposited onto indium tin oxide (ITO) electrodes and their electrochromic and fluorescence properties were investigated. Such films displayed color variation from yellow, in the neutral state, to green, in the oxidized state, as shown by tracking of the CIE (Commission Internationale de l’Eclairage) 1931 xy chromaticity coordinates. PFBT films are fluorescent in the neutral state (E = 0.0 V vs. Ag/Ag+) with emission at 532 nm; however, upon oxidation at 0.85 V the photoluminescence intensity is significantly decreased. A solid-state electrochromic device was assembled using PFBT and poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT-PSS) films and a polymer electrolyte. The device presented color variation from transmissive greenish-yellow to blue and reversible fluorescent properties upon switching between -1.5 to 1.5 V vs. PEDOT. Thus, the high contrast and stability both in electrochromism and electrofluorescence of the PFBT film and its device make them suitable for application in multifunctional optical devices.

本研究将一种名为PFBT的聚（芴-双噻吩）衍生物薄膜电沉积至氧化铟锡（indium tin oxide，简称ITO）电极表面，并对其电致变色与荧光性能展开了研究。通过追踪国际照明委员会（Commission Internationale de l’Eclairage，简称CIE）1931 xy色坐标可知，此类薄膜在中性态下呈黄色，氧化态下则转变为绿色，呈现出明显的颜色变化。PFBT薄膜在中性态（相对于Ag/Ag+电极的电位E=0.0 V）下具有荧光特性，发射波长为532 nm；但当在0.85 V电位下发生氧化反应后，其光致发光强度会显著降低。本研究采用PFBT薄膜、掺杂聚（苯乙烯磺酸钠）的聚（3,4-乙撑二氧噻吩）（poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate)，简称PEDOT-PSS）薄膜以及聚合物电解质，组装了一台固态电致变色器件。该器件在相对于PEDOT电极的-1.5 V至1.5 V电位区间内切换时，可实现从透射式绿黄色到蓝色的颜色变化，同时具备可逆的荧光性能。综上，PFBT薄膜及其器件在电致变色与电致荧光方面均表现出较高的对比度与稳定性，因此适用于多功能光学器件的应用场景。