Tracking Dynamic Doping in a Solid-State Electrochromic Device: Raman Microscopy Validates the Switching Mechanism

Solid-state electrochromic devices often need appropriate characterization to establish the real working mechanism for optimization and diagnosis. Raman mapping has been used here to track "dynamic doping", an important concept in organic electronics and in polythiophene-based solid-state electrochromic devices to understand and validate the mechanism of bias-induced redox-driven color switching. The proposed method demonstrates the live formation and movement of polarons which is best suited for in situ solid-state Raman spectroelectrochemistry. A 2-fold approach has been adopted here for this (1) by fabricating a working device in cross bar geometry followed by in situ spectroscopy to demonstrate the device functioning and (2) by carrying out Raman mapping from a device in custom-designed thin-film-transistor-like geometry to track and actually "see" the mechanism spectroscopically.