A double layer capacitor (DLC) containing at least one double layer capacitor cell is provided. Each double layer capacitor cell contains two current collectors, each containing a metallized carrier film with upper and lower planar surfaces, two thin electrode layers in direct contact with the lower and upper planar surfaces of the metallized carrier films of the first and second current collectors, and a polymer electrolyte layer in direct contact with the first and the second thin electrode layers. The polymer electrolyte is applied as a liquid which impregnates and encases the electrode layers and then solidified to form the electrolyte layer. The resulting DLC is preferably no thicker than about 20 microns, and may be as thin as 5 microns. Methods of producing a DLC and for forming a cross-linked electrolyte are also provided.