Development of visible and infrared electrochromic devices based on porous conducting polymers

Two of the research topics carried out in this dissertation were related to electrochromic materials and devices. The conducting polymer, poly (3,4-ethylenedioxythiophene), known as PEDOT, was used as the electrochromic element in these studies. The first objective in the research was to develop methods for decreasing the optical switching times of the devices. Since optical switching times are mainly governed by the diffusion of charge compensating counterions through the electrochromic layer, a more porous structure is expected to enhance the switching kinetics by increasing counterion diffusion. We synthesized porous PEDOT films by a galvanostatic electropolymerization method using high current densities. The visible wavelength electrochromic devices made with these materials exhibited switching times of less than 100 milliseconds. This is substantially faster than the ∼1 second switching times obtained with non-porous devices and clearly establishes that porous conducting polymers are able to achieve faster switching kinetics.; The second objective of this research was to fabricate electrochromic devices that were able to modulate infrared reflection in the 8 to 12 mum range. Upon doping the PEDOT, there was a substantial change in the refractive index of polymer layer which induced a large index mismatch with the substrate and produced high reflection from the substrate/polymer interface. The reflection modulation between the doped and undoped states was approximated using Fresnel's relation. The calculated values were in reasonable agreement with the experimental results. The anti-reflection coating on germanium minimized surface reflection and enabled us to achieve contrast ratios of greater than 5 between the doped and undoped states. The kinetics of infrared switching was also measured.; The third topic investigated in this dissertation is related to the emerging scientific area in which biology is integrated with nanoscience. The research was based on the vault protein which is a large protein nanocapsule that exists naturally in eukaryotic cells. We developed a novel method of forming a gold nanoparticle inside a vault by using UV activation. The expected size of the gold nanoparticle with varying gold ion concentration was calculated. Vaults containing gold nanoparticles by UV irradiation were characterized by transmission electron microscopy.