Oligo (ethylene glycol) side chain engineering: An efficient way for boosting the development of green-solvent processable electrochromic devices

Abstract

As an effective strategy for improving the performance of optoelectronic polymers, oligo (ethylene glycol) (OEG) side chain engineering has been widely used in optoelectronic materials field. However, the research of its impact on electrochromic (EC) polymers started to be explored in recent years. In this work, the excellent EC properties of the star polymer PTQ-10 (poly[(thiophene)-alt-(6,7-difluoro-2-(2-hexyldecyloxy)quinoxaline)]) were first investigated and proved. Subsequently, a series of novel PTQ-type polymers with OEG side chains (PTQ-OEGs) were successfully synthesized and studied. Compared with PTQ-10, the introduction of OEG side chains can significantly shorten the coloring time (∼82.2 %) and improve the coloration efficiency (∼37.3 %). Notably, the solubility of PTQ-OEGs is greatly enhanced in ideal green solvents (ethanol) via introducing the OEG side chains. Therefore, the EC active layers of PTQ-BTEG can be simply fabricated by its ethanol solution. Based on this feature, an all-green EC device PTQ-BTEG@ECD-3 (from material processing to device preparation) was prepared successfully, which exhibited fast coloring (6.25 s) and bleaching (0.85 s) as well as high coloration efficiency (622.57 cm2 C−1). Hence, we not only reported the relationship between OEGs and EC polymers thoroughly, but also proved the OEG engineering is a practical approach to promote the development of all-green EC devices in the near future.