The invention relates to an electrical device (1,20,30) comprising a cross-linked layer (3, 4, 5, 21, 22, 23, 31, 32) produced from a polymer composition comprising: at least one polymer A comprising at least one epoxy function; and a cross-linking agent B comprising at least one reactive function that can react with the epoxy function of said polymer A in order to allow the cross-linking of said polymer A. The device is characterised in that the polymer composition also comprises a compound C comprising: at least one aromatic group; and a reactive group that can physically interact with the hydroxyl function formed by the opening of said epoxy function during the cross-linking of polymer A.