An electro-chromic device including a solid or quasi-solid electrolyte layer is disclosed. The electrolyte layer may be a composite polymeric electrolyte layer. The polymeric electrolyte layer may be a conductive transparent adhesive or an optically transparent cured electrolyte. The electrolyte layer may also be a porous optically transparent membrane impregnated or embedded with an electrolytic material. Methods for forming solid or quasi-solid electrolyte layers in-situ in electro-chromic devices are also provided.