Abstract: The electrochromic element (20) comprises a substrate (28) and an electrochromic layer (25) having a thickness d on the basis of a metal oxide selected from the group formed by tungsten oxide, molybdenum oxide, niobium oxide, manganese oxide and zirconium oxide, or combinations thereof. The electrochromic layer (25) is characterized in that the oxygen content in the layer (25) varies across the thickness d of the layer (25). Preferably, the variation of the oxygen content in the layer (25) comprises at least two local maxima and a local minimum. Preferably, the electrochromic layer (25) is composed of a plurality of sub-layers (25', 25", 25'"), with the variation of the oxygen content in the layer (25) occurring predominantly at the location of transitions between two sub-layers. Preferably, the electrochromic layer (25) comprises the metal oxide tungsten oxide WO.sub.x. The electrochromic element may be provided on the display screen of a display device.

Abstract: A description is given of an electro-optical switching device (1) comprising a transparent substrate (3), a switching layer (5) of yttrium hydride as a first electrode, a palladium layer (7), an electrolyte layer of, e.g. Ta.sub.2 O.sub.5 (9), a layer of WO.sub.3 hydride as the second electrode (11), and a transparent ITO-layer (13). Under the influence of a potential difference or direct current between the electrodes (5) and (11), the yttrium hydride is electrochemically converted from a low-hydrogen-content state to a high-hydrogen-content state, or vice versa. The conversion between both compositions is reversible, and is accompanied by a change in optical transmission. Apart from Y, other trivalent metals may be used, such as Gd and La.