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Here in this work, a highly stable and flexible electrochromic film based on a composite of polyaniline and graphene quantum dots (PANI-fGQD), has been reported. To ensure the covalent attachment, monomer aniline was first attached to the negatively charged oxygenated groups present on the surface of GQDs followed by in-situ electrochemical polymerization for the composite. These amine sites act as nucleation sites for further growth. These electron rich oxygenated groups also act as secondary doping agents for hole dominating polyaniline (PANI). The prepared composite film has been found to show similar electrochemical response to that of PANI, but with more well-defined redox peaks and higher current densities. The composite (PANI-fGQD) exhibits improved electrochromic behavior with a color change from pale yellow to green to blue color as potential was scanned from −0.2 V to 0.8V. Pani-fGQD exhibits better optical contrast of 62% at 658nm and faster response time of 0.9s and 1.4s for coloration and bleaching, respectively, compared to pristine PANI. The composite also shows outstanding electrochemical stability of 15,000 cycles. The results present the significant potential of PANI-fGQD electrode for highly stable electrochromic application.

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Electrochromic devices have emerged as new age technology devices due their low power consumption, eye friendly working modes, and simple structure with easily adjustable features. Such devices have vast application prospects in areas like energy efficient building architecture, flexible displays, next generation smart wearables, satellite thermal control, etc. Organic electrochromic material offers several advantages, including rich color, stretchable and flexible architecture, facile synthesis, and easy modification of optical properties. However there are certain technical issues, such as cyclic stability, durability, uniform color performance, etc, which are still to be resolved before large scale commercialization of organic electrochromic devices can occur. In recent years, various research teams have made efforts in developing new methods and technologies to overcome such issues. Here, we have summarized these innovative efforts taken in the last decade to help researchers analyze and compare different techniques adopted toward improving the performance of organic electrochromic devices.