Quantification of electrochromic kinetics by analysis of RGB digital video images

Abstract

A new, rapid, and practical procedure to obtain quantitative kinetic information of electrochromic materials is proposed. When the transition between two colors on a colored electrode surface is monitorized by digital video, the analysis of pixel color intensity (I) in sequential RGB digital images allows us to precise the half-life time (t1/2) of the color change since a maximum value of the standard deviation of the pixel intensity (σ(I)) is reached. We simulated and analyzed the evolution of standard deviation during an electrochromic transition in different circumstances (kinetic and diffusion control). As an example of application, electrochromic transitions of a thin film model, the Prussian blue (PB), were digitally recorded during potential step chronoamperometry. From obtained t1/2, we calculated kinetic constants of the first order blue-to-transparent transition at different potential steps. The results suggest the great potential of this novel methodology to quantify the kinetics of electrochromic changes, even, in proof-of-concepts devices.