In-situ characterization of graphene based electrochromic devices

Electrochromic (EC) materials and electrolytes are the most imperative and active components in an electrochromic device (ECD). EC materials are able to reversibly change their light absorption properties in a certain wavelength range via redox reactions. It is highly desirable that the electrochromic device be flexible enough to grasp surfaces and be used in different optical fields. Grafen is one of the rare materials that have flexible properties as well as optical properties in three optical regions such as visible region, infrared and microwave region. In the thesis, multi layer grafen (MLG) electrodes were synthesized on nickel substratum at four different temperatures by chemical vapor deposition method. MLG electrodes that have four different thickness were obtained via change in the growth temperature. MLG electrodes were first transferred on polyvinyl chloride (PVC) and two different polyethylene substrates for flexible electrochromic device construction by thermal lamination and water bath. Characterizations of electrochromic devices formed using MLG electrodes were characterized by different measurement techniques, such as optical (FTIR and Raman spectroscopy), structural (X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray spectroscopy (EDX) and Atomic Force Microscopy (AFM)) life time (visible region detector) and electrical characterizations (four probe). According to optical measurements; As the thickness of the MLG electrodes increased, the intercalation voltage value increased, while the layer resistance decreased. In addition, as the applied potential increases, the optical permeability of the grafic electrodes increases, reaching the maximum at + 5V. In the second part, MLG electrode-based electrochromic devices formed using four different electrolytes with different anion and cation contents were characterized by varying electrolyte performance. Crystal structure analysis has been achieved to obtain the n-doping state of the resultant graphite, which requires a higher voltage value than the p-doping state.