Transparent photochromic device

A method for producing a transparent photochromic metal hydride device, the method comprising:

• using reactive sputtering to fabricate at least one photochromic yttrium hydride layer;
• incorporating oxygen into the at least one photochromic yttrium hydride layer;
• depositing a transparent capping layer on top of the at least one photochromic yttrium hydride layer;
• wherein the transparent photochromic metal hydride device comprises an essentially-hydrogen-impermeable transparent substrate, the at least one photochromic yttrium hydride layer, and the transparent capping layer, the at least one photochromic yttrium hydride layer having a band gap in the range from 1 eV to 4 eV without illumination, and the transparent capping layer at least partially positioned on an opposite side of the at least one photochromic yttrium hydride layer from the essentially-hydrogen-impermeable transparent substrate, the transparent capping layer being impermeable to hydrogen so as to maintain a concentration of hydrogen in the at least one photochromic yttrium hydride layer;
• wherein the thickness of the at least one photochromic yttrium hydride layer is in a range of 100-1500 nm;
• wherein the essentially-hydrogen-impermeable transparent substrate is a glass or polymer substrate;
• wherein the at least one photochromic yttrium hydride layer has an average oxygen concentration of approximately 30% to 65 at %;
• wherein the at least one photochromic yttrium hydride layer has a hydrogen concentration between 2 and 3 H per Y on the essentially-hydrogen-impermeable transparent substrate;
• wherein the transparent capping layer comprises at least one of a transition metal oxide, transition metal nitride, alkaline oxide, alkaline nitride, rare earth oxide, rare earth nitride, polymer and plastic;
• and
• wherein the transparent photochromic metal hydride device has a visual transparency in a clear state of greater than 50%.