The Effect of Oligo(Ethylene Oxide) Side Chains: A Strategy to Improve Contrast and Switching Speed in Electrochromic Polymers

Abstract

Solution‐processable electrochromic polymers (ECPs) with high performance are urgently needed for extensive applications. Nevertheless, they suffer from slow switching speed because of low ionic conductivities. Herein, we present an effective strategy to improve the contrast and switching speed in ECPs via facile side‐chain engineering. A novel electrochromic thieno[3,2‐b]thiophene‐based polymer (PmOTTBTD) is designed and successfully synthesized by introducing oligo(ethylene oxide) side chains with high ionic conductivity. Compared to the counterpart POTTBTD without modification by oligo(ethylene oxide) chains, PmOTTBTD demonstrates nearly double contrast (42 % vs. 24 %) with a fast oxidation switching process that just takes half of the time when detected under 400 nm, as well as much higher coloration efficiencies (e. g. 239.04 cm2 C−1 vs. 226.26 cm2 C−1 @ 400 nm and 314.04 cm2 C−1 vs. 174.00 cm2 C−1 @ 650∼700 nm). Besides, PmOTTBTD exhibits excellent stability with negligible decay after 3000 cycles. Our work suggests a facile strategy that could be adopted to realize high‐performance ECPs via molecular design tuning.

Ion Size-Dependent Electrochromism in Air-Stable Napthalenediimide-Based Conjugated Polymers

“…However, the t c and t b were 0.54 s and 1.0 s for Na + insertion/deinsertion at the same applied bias. We speculate that the rapid switching times observed for our films could have resulted from the preswelled state of the polymer, which facilitates efficient ion-transport pathways and ionic-electronic coupling . Although the polymer films interact with cations and display the expected color changes, a higher contrast (Δ T , %) of 45% was observed for Na + at −1.4 V compared to Li + (25%) or TEA + (18%) at −1.3 V (the bias that achieves maximum changes in the transmittance).…”

“…Appending oligoethylene glycol side chains to the backbone promotes the solvation of ions, polymer-dopant miscibility, and ion uptake and transport, properties that are central to achieving effective ionic-electronic coupling, high volumetric doping efficiencies, and faster electrochemical kinetics. In the context of electrochromic devices that operate volumetrically (i.e., the ions penetrate into the bulk of the polymer medium during the doping process), these metrics directly translate to enhanced optical modulation (Δ T %), high coloration efficiencies (CEs), and rapid coloration/bleaching times . However, there are no definitive design principles based on molecular structure for predicting cation transport in CPs, although the formation of TEG-cation chelates has been correlated with reduced cation transport. , Identifying design rules for modulating ion transport will not only benefit ECDs but, more widely, will assist the development of batteries with alternative cation insertion dynamics involving sodium and potassium …”

Design of Dithienopyran-Based Conjugated Polymers for High-Performance Electrochromic Devices

“…Although the response speed of ECDs is a crucial factor in dynamic applications such as information displays, papers focusing on improving ECD responsiveness are limited. 50,51 Electronic properties of ECPs may be the primary parameter affecting ECP performance, including dynamic response rates. Nonetheless, the correlation between the electronic and EC properties of ECPs has been rarely reported.…”

“…Therefore, it is expected that controlling the electronic properties of the conjugated polymer can be an effective strategy for tuning their optoelectronic characteristics and performance. Although the response speed of ECDs is a crucial factor in dynamic applications such as information displays, papers focusing on improving ECD responsiveness are limited. , Electronic properties of ECPs may be the primary parameter affecting ECP performance, including dynamic response rates. Nonetheless, the correlation between the electronic and EC properties of ECPs has been rarely reported.…”

An Efficient Electrochromic Supercapacitor Based on Solution‐Processable Nanoporous Poly{tris[4‐(3,4‐ethylenedioxythiophene)phenyl]amine}

“…Recently, Meng et al. synthesized several solution‐processable electrochromic conjugated polymers and Reynolds et al. evaluated the electrochromic properties of a series of homopolymers based on dioxythiophene with differently solubilizing side chains .…”