Ultrafast black color tunability of electrochromic dimming films using polyoxometalate-anchored metal oxide nanoparticles

Abstract

The fast switchable electrochromic (EC) materials have strong interest for controlling unnecessary lights from environment or achieving color tunability in transmissive-type and reflective-type display. In this study, a black color tunability of electrochromic dimming device was explored using polyoxometalate (PW)-anchored metal oxide (MOx) nanoparticles, poly(3,3-bis(bromomethyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine)s (PRBr), and an acid-free electrolyte layer. The PW-anchored MOx (PWMOx) layer was formed by electrostatic anchoring between the protonated MOx film and PW anion on a transparent electrode. The PWMOx was not only gave positive feedback to the electrochromic performance of its film, but also lowered the operating voltage by increasing the potential applied to the polymer layer in the electrochromic device, achieved black EC switching with high transparency modulation, a fast response time, and long endurance at a low operating voltage between 1.5 and -1.5 V. Furthermore, the boosted EC polymer properties arising from the charge balancing effect had the blocking capability for high-intensity light, such as 240 cd/m2 and ~ 2379 cd/m2 of light. The ECD blocked light transmission up to 95 % and dimming was adaptable to step voltage. This strategy may be coupled with various devices, including smart windows, transparent displays, image sensors, and augmented reality systems.