Quantitative Characterization of Optical Coupling in Nanoporous ZnO–WO₃ and ZnO–PEDOT Composite Electrodeposited Gratings Using Electrodiffraction Measurements

Abstract

To quantitatively characterize the optical coupling between ZnO (a high refractive index but nonabsorptive material) and an electrochromic material (either tungsten oxide (WO3) or poly­(3,4-ethylene­dioxythiophene) (PEDOT)), electrodiffractive and electrochromic properties were investigated from a novel two-component composite nanostructured electrodeposited grating that incorporated both ZnO and either WO3 or PEDOT. The sequential electrodeposition of these two materials through a photopatterned photoresist layer onto a fluorine-doped tin oxide (FTO)-coated glass substrate created a grating structure that exhibited optical diffraction that could be modulated electrochemically. SEM images of the electrochromic gratings revealed that the ZnO electrodeposition created a high surface area nanostructured thin film. The nanostructured ZnO is nonabsorbing, but its high refractive index and large surface area redirect light into the electrochromic grating and create a 4-fold enhancement in the grating’s electrodiffractive response.