Room-Temperature Spin-Coatable Polyoxometalate Composites for High-Contrast, Large-Area Electrochromic Capacitive Films

Abstract

Room-temperature spin-coatable polyoxometalate based composite is explored for low cost electrochromic capacitive film. Transparent stable K6P2W18O64 -polyvinyl alcohol (P2W18-PVA) solution was developed which suit for rigid and flexible substrates. The electrodeposited HKUST-1 particles were employed to create the pore structure in the film leading facile ion transportation. The excellent EC performance of P2W18 was fully expressed in this thin film with the thickness of 500 nm. The state-of-the-art record of 95% optical contrast and 1600 stable EC cycles are achieved. Electrochromic energy storage device with the capacity of 7.89 mF cm-2 was realized with MnO2 as counter electrode. This strategy for the preparation of highly stable and transparent POMs coating at room temperature is a general and simple solution that is not limited to the preparation of electrochromic films.