Counter electrode for electrochromic devices
The embodiments herein relate to electrochromic stacks, electrochromic devices, and methods and apparatus for making such stacks and devices. In various embodiments, an anodically coloring layer in an electrochromic stack or device is fabricated to include nickel tungsten tantalum oxide (NiWTaO). This material is particularly beneficial in that it is very transparent in its clear state.
1. A method of fabricating an electrochromic stack, the method comprising:
forming a cathodically coloring layer comprising a cathodically coloring electrochromic material; and
forming an anodically coloring layer comprising nickel tungsten tantalum oxide (NiWTaO),
wherein the NiWTaO has an atomic ratio of Ni:(W+Ta) is 1.8:1 to 3:1, and an atomic ratio of W:Ta is 1:1 to 2:1.
2. The method of claim 1 , wherein charge capacity of the NiWTaO is between 75 mC/cm 2 /micron and 200 mC/cm 2 /micron.
3. The method of claim 1 , wherein forming the anodically coloring layer comprises sputtering one or more sputter targets to form the NiWTaO.
4. The method of claim 3 , wherein at least one of the one or more of the sputter targets comprise an alloy comprising two or more metals selected from the group consisting of nickel, tungsten, and tantalum.
5. The method of claim 3 , wherein the anodically coloring layer is substantially amorphous.
6. The method of claim 3 , wherein the cathodically coloring layer and the anodically coloring layer are formed in direct physical contact with one another, without a separate ion conductor layer deposited between them, and further comprising converting a portion of the cathodically coloring layer and/or a portion of the anodically coloring layer to form an ion conducting and electrically insulating interfacial region between the cathodically coloring and anodically coloring layers.
7. The method of claim 3 , wherein the anodically coloring layer comprises two or more sub-layers that have different compositions and/or morphologies.
8. The method of claim 3 , wherein the cathodically coloring electrochromic material comprises tungsten oxide.
9. The method of claim 3 , wherein the cathodically coloring layer comprises a bilayer or a graded layer, and wherein a portion of the cathodically coloring layer is superstoichiometric with respect to oxygen.
10. An electrochromic device stack, comprising:
a cathodically coloring layer comprising a cathodically coloring material; and
an anodically coloring layer comprising nickel tungsten tantalum oxide
wherein the nickel tungsten tantalum oxide has an atomic ratio of Ni:(W+Ta) that is between 1.8:1 and 3:1, and has an atomic ratio of W:Ta that is between 1:1 and 2:1.
11. The electrochromic device stack of claim 10 , wherein charge capacity of the NiWTaO is between 75 mC/cm 2 /micron and 200 mC/cm 2 /micron.
12. The electrochromic device stack of claim 10 , wherein the anodically coloring layer is substantially amorphous.
13. The electrochromic device stack of claim 10 , wherein the anodically coloring layer comprises two or more sub-layers having different compositions and/or morphologies.
14. The electrochromic device stack of claim 10 , wherein the cathodically coloring material comprises tungsten oxide.
15. The electrochromic device stack of claim 10 , wherein the cathodically coloring layer comprises a bilayer or a graded layer, and wherein a portion of the cathodically coloring layer is superstoichiometric with respect to oxygen.
16. An integrated deposition system for fabricating an electrochromic device stack, the integrated deposition system comprising:
a plurality of deposition stations aligned in series and interconnected and operable to pass a substrate from one station to the next without exposing the substrate to an external environment,
wherein the plurality of deposition stations comprise
(i) a first deposition station containing one or more material sources for depositing a cathodically coloring layer;
(ii) a second deposition station containing one or more material sources for depositing an anodically coloring layer comprising nickel tungsten tantalum oxide,
wherein the nickel tungsten tantalum oxide has an atomic ratio of Ni:(W+Ta) that is between 1.8:1 and 3:1, and has an atomic ratio of W:Ta that is between 1:1 and 2:1; and
a controller containing program instructions for passing the substrate through the plurality of deposition stations in a manner that deposits on the substrate (i) the cathodically coloring layer, and (ii) the anodically coloring layer to form a stack comprising at least the cathodically coloring layer and the anodically coloring layer.
17. The integrated deposition system of claim 16 , wherein charge capacity of the NiWTaO formed is between 75 mC/cm 2 /micron and 200 mC/cm 2 /micron.
18. The integrated deposition system of claim 16 , wherein at least one of the second one or more material sources for depositing the anodically coloring layer comprise an elemental metal selected from the group consisting of: nickel, tungsten, and tantalum.
19. The integrated deposition system of claim 16 , wherein at least one of the second one or more material sources for depositing the anodically coloring layer comprise an alloy comprising two or more metals selected from the group consisting of: nickel, tungsten, and tantalum.
20. The integrated deposition system of claim 16 , wherein at least one of the second one or more material sources for depositing the anodically coloring layer comprise an oxide.
21. The integrated deposition system of claim 16 , wherein the controller comprises instructions for passing the substrate through the plurality of deposition stations in a manner that deposits the anodically coloring layer as a substantially amorphous material.
22. The integrated deposition system of claim 16 , wherein the controller comprises instructions for passing the substrate through the plurality of deposition stations in a manner that (1) deposits the cathodically coloring layer and the anodically coloring layer in direct physical contact with one another, and (2) converts a portion of the cathodically coloring layer and/or a portion of the anodically coloring layer to form an ion conducting and electrically insulating interfacial region between the cathodically coloring layer and the anodically coloring layer.
23. The integrated deposition system of claim 16 , wherein the controller contains program instructions for depositing the anodically coloring layer as two or more sub-layers having different compositions and/or morphologies.
24. The integrated deposition system of claim 16 , wherein the cathodically coloring layer comprises tungsten oxide WOx, wherein x is at least about 2.7 and is less than 3.0.
25. The integrated deposition system of claim 16 , wherein the cathodically coloring layer comprises a bilayer or a graded layer, and wherein a portion of the cathodically coloring layer is superstoichiometric with respect to oxygen.
26. A composition of matter comprising:
(a) nickel;
(b) tungsten;
(c) tantalum; and
(d) oxygen,
wherein the composition of matter comprises an atomic ratio of Ni:(W+Ta) that is between about 1.8:1 and 3:1, and an atomic ratio of W:Ta that is between about 1:1 and 2:1.
27. The composition of matter of claim 26 , wherein charge capacity of the NiWTaO is between 75 mC/cm 2 /micron and 200 mC/cm 2 /micron.
28. The composition of matter of claim 26 , wherein the composition of matter is provided as an amorphous matrix with nanocrystals distributed throughout, wherein the nanocrystals have a mean diameter of about 50 nm or less.