Temperable electrochromic devices
This disclosure provides systems, methods, and apparatus for tempering or chemically strengthening glass substrates having electrochromic devices fabricated thereon. In one aspect, an electrochromic device is fabricated on a glass substrate. The glass substrate is then tempered or chemically strengthened. The disclosed methods may reduce or prevent potential issues that the electrochromic device may experience during the tempering or the chemical strengthening processes, including the loss of charge carrying ions from the device, redistribution of charge carrying ions in the device, modification of the morphology of materials included in the device, modification of the oxidation state of materials included in the device, and the formation of an interfacial region between the electrochromic layer and the counter electrode layer of the device that impacts the performance of the device.
1. A method of fabricating an electrochromic device on a glass substrate having a first transparent conducting oxide layer disposed thereon, the method comprising:
a) forming a stack on the first transparent conducting oxide layer, the stack comprising:
(i) an electrochromic layer comprising an electrochromic material; and
(ii) a counter electrode layer comprising a counter electrode material;
b) forming a second transparent conducting oxide layer on top of the stack;
c) forming a capping layer on top of the second transparent conducting oxide layer, wherein the capping layer includes an oxygen diffusion barrier configured to reduce oxygen diffusion into, and out of, the stack during tempering; and then
d) tempering the glass substrate after operation c).
2. The method of claim 1 , further comprising introducing lithium to the stack in excess of that required for the electrochromic device to operate in transitioning between optical states.
3. The method of claim 2 , wherein the lithium is introduced to the stack prior to c).
4. The method of claim 1 , further comprising forming a diffusion barrier on the glass substrate prior to a).
5. The method of claim 4 , wherein the diffusion barrier is a lithium diffusion barrier and/or a sodium diffusion barrier.
6. The method of claim 1 , wherein tempering the glass substrate is performed in an inert atmosphere.
7. The method of claim 1 , wherein the capping layer includes a material selected from the group consisting of silicon dioxide, silicon aluminum oxide, silicon nitride, and silicon oxynitride.
8. The method of claim 1 ,
wherein forming the stack comprises forming the electrochromic layer and/or the counter electrode layer having a first morphology, and
wherein tempering the glass substrate transforms the first morphology of the electrochromic layer and/or the counter electrode layer.
9. The method of claim 1 , wherein the electrochromic material, the counter electrode material, the first transparent conducting oxide layer, and the second transparent conducting oxide layer have substantially similar coefficients of thermal expansion.
10. The method of claim 1 , wherein the capping layer is a sacrificial layer that is removed after tempering the glass substrate.
11. The method of claim 10 , wherein the sacrificial layer is opaque.
12. The method of claim 1 , wherein the capping layer comprises a material selected from the group consisting of silicon, titanium, and aluminum.
13. The method of claim 1 , wherein the capping layer comprises at least one of a lithium metal material, a lithium alloy material, and a lithium intermetallic material.
14. The method of claim 13 , wherein tempering the glass substrate drives lithium from the capping layer into the stack.
15. The method of claim 10 , wherein the capping layer is removed using a process selected from the group consisting of a chemical etching process with hydrofluoric acid, a plasma etching process, an ion milling process, a laser ablation process, an exposure to radiation process, and an applying shear forces process.
16. The method of claim 13 , wherein the capping layer is further configured to prevent lithium from leaving the stack while tempering the glass substrate.
17. The method of claim 1 , wherein the capping layer is configured to seal the electrochromic device hermetically.
18. The method of claim 1 , wherein the capping layer comprises a protective oxide or nitride layer.
19. The method of claim 1 , wherein the capping layer is substantially transparent.
20. The method of claim 1 , wherein the capping layer comprises a low-emissivity material.
21. The method of claim 1 , wherein the capping layer comprises an anti-reflective material.