Pixel-Level Image-Based Analysis of Spatial Kinetics and Resistance Variation in a Large-Area Electrochromic Device

High Resolution Image Download MS PowerPoint Slide Electrochromic (EC) materials and devices (ECDs) have been extensively studied, providing valuable insight into their optical switching properties and material characteristics. To analyze dynamic and subtle spatial variations during switching, we developed for the first time a noninvasive, automated, image-based methodology capable of resolving EC behavior at the pixel level. Grayscale images, extracted from video recordings at 0.0333 s intervals during cyclic operation, were segmented into 8,448 localized pixel positions to quantify contrast–time profiles. First, switching nonuniformity was visualized, revealing reaction times from 0.8 to 2.0 s to reach 90% contrast change, with faster responses at the edges and slower transitions in the center. Second, segmental kinetics were evaluated by fitting time constants (τ) to each profile and linking them to composite resistances using a simplified RC model with a uniform areal capacitance (0.0133 F cm –2 ). The edge segment exhibited lower τ (1.79) and resistance (134.5 Ω·cm 2 ), whereas the central pixel position showed delayed switching (1.80 s) with larger τ (2.46) and higher resistance (184.9 Ω·cm 2 ). Finally, spatial distributions were visualized through 2D heat maps, confirming slower central regions (1.60–1.95 s), with regional average resistance of 185.7 Ω·cm 2 compared to lower-resistance peripheral regions (136.8–149.6 Ω·cm 2 ). This noninvasive approach enables a high-resolution diagnostic platform for quantifying uniformity, kinetics, and resistance distributions in large-area ECDs and is broadly applicable to diverse EC architectures influenced by spatial transport effects.