Solid polymer electrolytes (SPE) based on ionic liquid, poly-(vinylidene fluoride) and solvent N-methyl-pyrrolidone represent an effective component in electrochemical sensors. The advantage lies in their composition, which offers an opportunity to prepare SPE layers with a different porosity and microstructure. The study shows how the SPEs of different crystallinities affect the performance of an amperometric gas sensor from the point of view of current response (sensitivity), limit of detection and current fluctuations. The morphology of SPE has an impact not only on its conductivity but also on sensor sensitivity due to the morphology of the interface SPE/working electrode (WE).