Rational Molecular Design of Electrochromic Conjugated Polymers: Toward High-Performance Systems with Ultrahigh Coloration Efficiency
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초록
내용
We propose a series of reasonably designed π-conjugated polymers (CPs) for high performance electrochromic devices (ECDs). The principle of molecular design includes the introduction of a fused aryl amine (e.g., indolocarbazole or indoloindole) to effectively modify the optical and electrical characteristics of CPs, leading to high redox stability with fast response and high coloration efficiency (η). The resulting ECD with the fluorinated indoloindole-based CP exhibits the highest overall performance with rapid response time, a large ∆T of ∼46%, an outstanding η of ∼1563.3 cm2/C, and a reliable operation stability even after 6,500 cycles. We elucidate the origin of superb performance by calculating redox rate constants of CPs via Nicholson method and determining their thin film crystalline structures using GI-XRD. In addition, the ultrahigh cyclic stability is explained by predicting the degree of molecular distortions of CPs during redox reactions through DFT calculation.