Electrically controllable device having variable optical/energy properties in transmission or in reflection, comprising at least one carrier substrate provided with a stack of electrochromic functional layers, including at least two electrochromic active layers, separated by an electrolyte, said stack being placed between two current leads, namely the lower current lead and the upper current lead respectively ("lower" corresponding to the current lead closest to the carrier substrate, as opposed to the "upper" current lead which is furthest from said substrate), characterized in that the electrochromic material constituting the two active layers is identical, and this electrochromic material is chosen from those whose coloration is not a linear function of the charge insertion.