Prof. Cai research group achieved great progress in large area electrochromic films and devices recently. The corresponding paper are published in the ACS Energy Letters, entitled "Molecular Level Assembly for High Performance Flexible Electrochromic Energy Storage Devices". (ACS Energy Lett., 2020, 5, 1159-1166, IF = 16.331).

Electrochromic devices can persistently change their optical properties and revert to the original state upon application of an alternating small voltage, which has attracted much attention because of its low-power consumption and broad fascinating applications, such as energy-efficient information displays, electronic labels, smart windows, switchable mirrors, and other cutting-edge applications. However, it remains extremely challenging to construct rational nanoarchitectures at the molecular level by simple and low-cost methods for high-performance and scalable electrochromic films.

In this work, the authors fabricated large-area flexible electrochromic films (810 cm2) on flexible and rigid substrates based on PolyFe by utilizing electrostatic spraying technology. The prepared PolyFe thin film exhibits excellent electrochromic properties, such as ultra-high coloring efficiency (750.3 cm2 C−1), ultra-fast coloring speed (<1s), and robust cyclic stability (optical modulation range without significant attenuation after 10,000 cycles).

Based on this kind of high-performance electrochromic film, a multi-functional flexible electrochromic energy-storage device was assembled, which integrates the dynamic dimming control and energy-storage application at the same time. The fabricated device has good performance, and the energy-storage level is visually perceptible and recognizable in real time. Moreover, this color-changing energy-storage device can recover and reuse the energy consumed during the color-changing process. This multifunctional device has promising applications in self-powered display, color-changing skin, and energy storage display.

Dr. Cai Guofa, Key Laboratory of Special Functional Materials, is the first author of the paper. Dr. Lee Pooi See, Professor, Nanyang Technological University, Singapore, and Dr. Masayoshi Higuchi, National Institute of Materials Science, Japan, are co-corresponding authors. This work is supported by Nanyang Technological University in Singapore, National Institute of Materials Science in Japan, Henan Provincial Department of Science and Technology, Henan Provincial Department of Education and Henan University.

PolyFe electrochromic films and their electrochromic properties prepared based on molecular assembly electrostatic spraying technology