Abstract Isoindigo, an electron deficient heteroaromatic compound, was developed as a great potential building block in the construction of low bandgap conjugated polymers with enhanced optoelectronic performances. Herein, via the Donor–Acceptor approach, a novel range of conjugated copolymers were rationally designed and synthesized by employing isoindigo as acceptor, electron rich fused thiophenes (i.e. thieno[3,2-b]thiophene, cyclopentadithiophene) as donors. The polymeric films can be easily obtained via spray-coating method due to their excellent solubility in common solvent. The optoelectronic properties of these copolymers were detailedly studied by electrochemical and spectroelectrochemical methods. Owing to the alternating donor–acceptor structure in the polymer backbones, as-prepared copolymers showed outstanding reversible redox activity and stability as well as tunable spectroscopic properties (e.g. bandgaps, colors) depending on the composition (i.e. D–A ratio) of the copolymers. These polymeric films demonstrated low bandgaps (Eg) ranging from 1.50 to 1.53 eV. Importantly, the as-prepared films revealed distinct electrochromic switching behaviors. Highly enhanced electrochromic performance, such as high optical contrast (56.9–80.8%), fast response time (0.36–0.94 s) and high coloring efficiency (300–466.67 cm2 C−1) were found for the polymeric films in the visible or near-IR region due to the rationally designed D–A structure. Furthermore, these polymeric films showed remarkable thermal stability. All the above features make this kind of D–A typed copolymers a promising candidate for the electrochromic application.

中文翻译：

---

新型异靛蓝基供体-受体型低带隙共轭聚合物作为溶液加工高性能电致变色材料的合理设计

摘要 Isoindigo 是一种缺电子的杂芳族化合物，被开发为具有增强光电性能的低带隙共轭聚合物的潜在构建块。在此，通过供体-受体方法，通过采用异靛蓝作为受体，富电子稠合噻吩（即噻吩并[3,2-b]噻吩，环戊二噻吩）作为供体，合理设计和合成了一系列新型共轭共聚物。由于聚合物薄膜在普通溶剂中具有优异的溶解性，因此可以通过喷涂方法轻松获得。通过电化学和光谱电化学方法详细研究了这些共聚物的光电性能。由于聚合物骨架中交替的供体-受体结构，所制备的共聚物显示出出色的可逆氧化还原活性和稳定性以及可调的光谱特性（例如带隙、颜色），具体取决于共聚物的组成（即 D-A 比率）。这些聚合物薄膜表现出范围从 1.50 到 1.53 eV 的低带隙 (Eg)。重要的是，所制备的薄膜显示出不同的电致变色开关行为。在可见光或近光处发现聚合物薄膜具有高度增强的电致变色性能，例如高光学对比度 (56.9–80.8%)、快速响应时间 (0.36–0.94 s) 和高着色效率 (300–466.67 cm2 C-1) -IR 区域由于合理设计的 D-A 结构。此外，这些聚合物薄膜表现出显着的热稳定性。