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 a heterogeneous structure, for example a heterogeneous composition and/or morphology. Such heterogeneous anodically coloring layers can be used to better tune the properties of a device.
1 . A method of fabricating an electrochromic stack, the method comprising:
depositing a first electrochromic (EC) sublayer of an EC layer comprising a cathodically tinting electrochromic material;
depositing a second EC sublayer of the EC layer; and
depositing a counter electrode (CE) layer;
wherein the CE layer consists of a single layer with a composition gradient increasing in a direction away from the EC layer, thereby enabling controlled release of ions from different depths within the CE layer based on applied voltage.
2 . The method of claim 1 , wherein the first EC sublayer, the second EC sublayer, and the CE layer are deposited in an integrated deposition system including only one lithiation station.
3 . The method of claim 1 , wherein each EC sublayer comprises a cathodically coloring electrochromic material.
4 . The method of claim 3 , wherein the cathodically coloring electrochromic material comprises tungsten oxide.
5 . The method of claim 1 , wherein one sublayer of the first and second EC sublayers is oxygen rich compared to the other sublayer of the first and second EC sublayer, the oxygen rich sublayer being proximal to the CE layer.
6 . The method of claim 1 , wherein the first or second EC sublayer is a flash layer not thicker than 100 nm.
7 . The method of claim 1 , wherein the CE layer comprises an anodically coloring electrochromic material.
8 . The method of claim 7 wherein the anodically coloring electrochromic material comprises a nickel tungsten oxide composition.
9 . The method of claim 1 , wherein depositing a CE layer comprises depositing the CE layer using a CE target.
10 . The method of claim 9 , wherein the CE target is a ceramic target.
11 . The method of claim 10 , wherein the ceramic target comprises a nickel tungsten oxide composition.
12 . The method of claim 10 , wherein the ceramic target comprises lithium.
13 . The method of claim 12 , wherein the ceramic target comprises a lithium nickel tungsten tantalum oxide composition.
14 . The method of claim 1 , further comprising heating the electrochromic stack.
15 . The method of claim 1 wherein depositing the CE layer comprises sputtering with differential oxygen concentrations to form a morphology gradient in the CE layer.
16 . The method of claim 1 wherein the CE layer comprises NiWO between about 150 nm and about 300 nm thick.
17 . The method of claim 16 wherein the NiWO is substantially amorphous.
18 . The method of claim 1 further comprising sputtering lithium onto the CE layer until the CE layer is substantially bleached.
19 . The method of claim 18 further comprising sputtering an additional amount of lithium, between about 5% and about 15% excess based on the quantity required to bleach the CE layer, onto the CE layer.
20 . The method of claim 18 wherein a morphology of the CE layer varies from crystalline to amorphous.
21 . The method of claim 1 wherein the CE layer consists of a single layer with both a composition gradient and a morphology gradient.