Spontaneously Spreading a Conjugated Polymer Film to Construct a Multifunctional Electrochromic Device with Tunable Color

Conjugated polymers as electrochromic materials possess large application markets in flexible electronics due to their outstanding properties. However, obtaining high-quality polymer films through sample methods remains a bottleneck for commercial products. In this study, we leveraged the advantages of the spontaneous spreading technique (SS) to fabricate uniform electrochromic polymer films based on PTT. PTT prepared via SS (PTT-SS) possesses a lower oxidation potential and better stability than that prepared by spray-coating (PTT-SC). And PTT-SS exhibits improved electrochromic properties (ΔT = 64%) relative to PTT-SC (ΔT = 51%). In addition, SS could effectively avoid the frosted appearance of polymer films prepared by SC. Through layer-by-layer stacking of different polymer films prepared by SS, a composite polymer film (ETTB/PTT) could achieve more colors at different applied potentials than pure polymer films. Interestingly, layer-by-layer stacking by SS retains the photoluminescence of ETTB, leading to ETTB/PTT exhibiting obvious electrofluorochromic performance during the redox process. The strategy provides an opportunity for constructing multifunctional electrochromic polymer films with tunable colors.