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

A black color tunability of an electrochromic (EC) dimming device was explored using cobalt polyoxometalate (CoPW)-anchored nickel oxide nanoparticles (CoPW@NiOx). The CoPW@NiOx layer enhanced not only the anodic EC properties of NiOx but also the cathodically coloring EC polymer (poly(3,3-bis(bromomethyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine)) arising from the charge balancing effect boosted by CoPW. In particular, PCN400 with a 400 nm-thick CoPW@NiOx layer, achieved black EC switching with high transparency modulation from 73% to 3%, a response time of 0.4 s, and long endurance of over 3000 cycles at a low operating voltage between 1.5 and −1.5 V. PCN400 blocked light transmission up to 95%, and dimming was adaptable to voltage steps, even under an intense light exposure of 2379 cd cm⁻². These adaptable EC devices afforded visual comfort for a display and convertible functionality between the AR and VR. Thus, PCN400 could be coupled with various devices, including smart windows, transparent displays, image sensors, and augmented reality systems.