Flexible electrochromic thin films with ultrafast responsion based on exfoliated V_2O_5 nanosheets/graphene oxide via layer-by-layer assembly

摘要

Flexible electrochromic (EC) display devices have received extensive attention due to their application in the new generation of smart and wearable devices. 2D ultrathin nanosheets are the promising structure to allow EC materials (such as V2O5, WO3) to be incorporated into flexible EC electronics owing to their surface-to-surface contact with the flexible substrate. Herein, the graphene-like V2O5 nanosheets (V2O5 NSs) with thicknesses ranging from few-layers (4 nm) to 40 nm are synthesized by liquid-phase exfoliation (LPE) method. To enhance the electronic conductivity and decrease the agglomeration of V2O5 NSs, graphene oxide (GO) is introduced to fabricate V2O5 NSs/GO films by layer-by-layer (LBL) assembly method. The composite films exhibit ultrafast coloring responsion time (1.6 s) and bleaching time (2 s) attributed to the reduced charge transport distances of 2D ultrathin structure. The LBL assembly structure accompanied by larger Li+ ions storage surface areas facilitates the superior transmittance contrast (Delta T) of 57.5% at 425 nm and reversible yellow/green/blue-grey color changes. Besides, the flexible V2O5 NSs/GO films on ITO/PET substrate still display rapid responsion speed (2.7 s/4.3 s) after bending 100 cycles with the bending angle of 90 degrees, which manifests their potentially application for flexible EC devices.