Enhancing Electrochromic Stability of Triphenylamine-Based Polymers via Monomer Ratio Optimization

In the pursuit of high-performance organic electrochromic
(OEC)
materials that transition from transparent to deep colors, we design
and synthesize a series of copolymerstermed MeTmPhFncomposed of TPA and fluorene with triethylene
glycol and ester groups incorporated. This is achieved through gradient
tuning of monomer ratios via Suzuki copolymerization. Five of these
polymers exhibit excellent film-forming properties, and their electrochromic
devices demonstrate remarkable pale blue-to-reddish brown switching
behavior. Notably, benefiting from the suitable continuity and moderate
porosity of MeT0.5PhF0.5 film, the electrochromic
device based on MeT0.5PhF0.5 showcases rapid
reversible switching times of 2.5 s for coloring and 1.3 s for bleaching,
highlighting its exceptional responsiveness. This device achieves
the highest contrast of 58.7% at 465 nm, paired with impressive cycling
stability, retaining 93.7% of its initial contrast ratio after 1440
cycles, and exhibits a high coloration efficiency of 619 cm2 C–1. This study presents an effective approach
for designing and synthesizing high-performance electrochromic copolymers
that effectively transition from colorless to vibrant hues, paving
the way for advanced applications in smart windows and display technologies.