This invention discloses a process for assembling an electrooptic (including electrochromic) devices, wherein the device comprises a step of forming solid electrolyte layer by in-situ polymerization of a liquid composition wherein the said liquid composition comprises at least one ionic liquid. The polymerization process may lead to formation of a crosslinked polymer, and such a process may be initiated by UV radiation. The electrochromic devices of this invention may be used as a display, window or a variable reflectivity automotive mirror.