01729nas a2200145   4500008004100000050001500041245004700056210004700103260002900150520125500179100002701434700002401461700002301485856007501508       2000                        eng d  aLBNL-4651000aElectrochromism in Copper Oxide Thin Films0 aElectrochromism in Copper Oxide Thin Films  aUppsala, Swedenc08/20003 a<p>Transparent thin films of copper(I) oxide prepared on conductive SnO<sub>2</sub>:F glass substrates by anodic oxidation of sputtered copper films or by direct electrodeposition of Cu<sub>2</sub>O transformed reversibly to opaque metallic copper films when reduced in alkaline electrolyte. In addition, the same Cu<sub>2</sub>O films transform reversibly to black copper(II) oxide when cycled at more anodic potentials. Copper oxide-to-copper switching covered a large dynamic range, from 85% and 10% photopic transmittance, with a coloration efficiency of about 32 cm<sup>2</sup>/C. Gradual deterioration of the switching range occurred over 20 to 100 cycles. This is tentatively ascribed to coarsening of the film and contact degradation caused by the 65% volume change on conversion of Cu to Cu<sub>2</sub>O. Switching between the two copper oxides (which have similar volumes) was more stable and more efficient (CE = 60 cm<sup>2</sup>/C), but covered a smaller transmittance range (60% to 44% T). Due to their large electrochemical storage capacity and tolerance for alkaline electrolytes, these cathodically coloring films may be useful as counter electrodes for anodically coloring electrode films such as nickel oxide or metal hydrides.</p>1 aRichardson, Thomas, J.1 aSlack, Jonathan, L.1 aRubin, Michael, D.  uhttps://facades.lbl.gov/publications/electrochromism-copper-oxide-thin