Polymer-based electrochromic smart windows are an emerging energy-saving technology. There are several technological hurdles in the development of organic electrochromics. In this article, the self-bleaching behaviors of a black electrochromic polymer (ECP-black) thin film were investigated. We found that the electrochemical break-in process led to a less dense morphology and the increased free volume facilitated ion permeation in the ECP-black thin films. The polarized interface between the polymer thin film and transparent indium-tin-oxide (ITO) electrode made charge transfer accessible, which caused the self-bleaching behaviors. Herein, we proposed two approaches to study and mitigate the self-bleaching phenomenon. First, a densely packed morphology was regenerated by increasing the cathodic polarization time under open-circuit conditions (V_off). The second involved the modification of the electrode (ITO) surface with a partial coverage of the octadecyltrichlorosilane layer. The combination of the two approaches rendered the ECP-black thin film capable of maintaining the colored state for up to 900 s. To extend the scope of our studies, self-bleaching of ECP-magenta and ECP-blue thin films were also tested and suppressed by using these two methods. Additionally, the cycling stability of the ECP-black has been improved from ∼600 cycles to up to 2300 cycles without a noticeable decay of optical contrast.

中文翻译：

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黑色至透射电致变色聚合物薄膜中的自漂白行为

基于聚合物的电致变色智能窗户是一种新兴的节能技术。在有机电致变色材料的开发中存在若干技术障碍。在本文中，研究了黑色电致变色聚合物（ECP黑色）薄膜的自漂白行为。我们发现电化学闯入过程导致较低的形态，而增加的自由体积则促进了ECP黑色薄膜中的离子渗透。聚合物薄膜和透明的氧化铟锡（ITO）电极之间的极化界面使电荷转移变得容易进行，这导致了自漂白行为。在此，我们提出了两种方法来研究和减轻自漂白现象。首先，通过增加开路条件下的阴极极化时间，可以再生出致密的形态（V _off）。第二个涉及用十八烷基三氯硅烷层的部分覆盖来修饰电极（ITO）表面。两种方法的结合使ECP黑色薄膜能够在长达900 s的时间内保持着色状态。为了扩展我们的研究范围，还使用这两种方法测试并抑制了ECP-品红色和ECP-蓝色薄膜的自漂白。此外，ECP黑色的循环稳定性已从约600个循环提高到了2300个循环，而光学对比度却没有明显下降。