ENERGY STORAGE DEVICE

An energy storage device, includes a substrate having a portion that is optically transparent in a predefined range of wavelengths, and at least one electrochemical energy storage system comprising, as from a face of the transparent portion, a stack having successively a first current collector, a first electrode, an electrolyte, a second electrode and a second current collector, the stack being covered partially by a cover characterised in that wherein at least one part of the cover has a coefficient of light absorbance greater than or equal to %, and preferably greater than %.