Thin film lithium tungsten oxides for electrochromic applications and methods of making the same
An electrochromic multi-layer stack is provided. The electrochromic multi-layer stack includes a thin film that includes lithium tungsten oxide with lithium included in the fully bleached state. The electrochromic multi-layer stack also includes an electrically conductive layer, and an outer substrate. An electrochromic device is also provided.
1. An electrochromic device comprising:
a thin film comprising lithium tungsten oxide with the formula Li x WO 3+y wherein x is greater than 0 and less than or equal to 1, and y is greater than 0 and less than or equal to 0.5 in the fully bleached state;
an electrically conductive layer; and
an outer substrate,
wherein the electrochromic device has a Tvis greater than 60% in the fully bleached state.
2. The electrochromic device of claim 1 , further comprising:
L* from 80 to 100 in the fully bleached state;
a* from −10 to 10 in the fully bleached state; and
b* from −5 to 5 in the fully bleached state.
3. The electrochromic device of claim 1 , further comprising:
b* from −5 to 5 in the fully bleached state.
4. The electrochromic device of claim 1 , further comprising:
a darkened state Tvis less than 5%.
5. The electrochromic device of claim 1 , further comprising:
a difference in device charge capacity of between −2% and 2%, when the device is cycled from a bleached state to a darkened state and back to the bleached state 1000 times, at 85° C., and exposed to illumination approximating the solar spectrum with an intensity of approximately 1000 W/m 2 .
6. The electrochromic device of claim 1 , further comprising:
a difference in device charge capacity from a loss of 4 mC/cm 2 to a gain of 4 mC/cm 2 , when the device is cycled from a bleached state to a darkened state and back to the bleached state 1000 times, at 85° C., and exposed to illumination approximating the solar spectrum with an intensity of approximately 1000 W/m 2 .
7. The electrochromic device of claim 1 , further comprising:
a difference in device b* of between −3.5 and 1, when the device is cycled from a bleached state to a darkened state and back to the bleached state 1000 times, at 85° C., and exposed to illumination approximating the solar spectrum with an intensity of approximately 1000 W/m 2 .
8. The electrochromic device of claim 1 , further comprising:
a difference in device Tvis of between −20% and 0%, when the device is cycled from a bleached state to a darkened state and back to the bleached state 1000 times, at 85° C., and exposed to illumination approximating the solar spectrum with an intensity of approximately 1000 W/m 2 .
9. A process for preparing a multi-layer electrochromic structure, the process comprising:
providing an outer substrate;
depositing an electrically conductive layer on the outer substrate;
providing a liquid mixture comprising:
a liquid phase;
a dispersed phase;
lithium; and
tungsten;
depositing the liquid mixture onto a surface of the electrically conductive layer to form a thin film; and
thermally treating the thin film to form a treated lithium tungsten oxide cathodic electrochromic layer, wherein the treated lithium tungsten oxide cathodic electrochromic layer comprises lithium tungsten oxide with the formula Li x WO 3+y wherein x is greater than 0 and less than or equal to 1, and y is greater than 0 and less than or equal to 0.5 in the fully bleached state, and
wherein the electrochromic structure has a Tvis greater than 60% in the fully bleached state.
10. The process of claim 9 , wherein the lithium incorporated in the as-deposited treated lithium tungsten oxide cathodic electrochromic layer in the fully bleached state does not donate electrons to the tungsten atoms.
11. The process of claim 9 , wherein the lithium incorporated in the as-deposited treated lithium tungsten oxide cathodic electrochromic layer in the fully bleached state does not convert W 6+ to W 5+ in the treated lithium tungsten oxide cathodic electrochromic layer.
12. The process of claim 9 , wherein the treated lithium tungsten oxide cathodic electrochromic layer comprises a perovskite crystal structure.
13. The process of claim 9 , wherein the treated lithium tungsten oxide cathodic electrochromic layer has a perovskite crystal structure with a space group P4/nmm.
14. The process of claim 9 , wherein the treated lithium tungsten oxide cathodic electrochromic layer has a perovskite crystal structure with a space group P4/nmm, and lattice parameters of a=b=from approximately 5.2 angstroms to approximately 5.3 angstroms, and c=from approximately 3.8 angstroms to approximately 3.9 angstroms.
15. The process of claim 9 , wherein the treated lithium tungsten oxide cathodic electrochromic layer has Raman peaks at approximately 805 cm −1 , at approximately 950 cm −1 , at approximately 680-715 cm −1 , and at approximately 270 cm −1 .
16. The process of claim 9 , wherein the thermal treatment comprises hydrolyzing and calcining the thin film.
17. The process of claim 9 , wherein the thermal treatment comprises annealing the thin film at a temperature from 300° C. to 650° C., for a duration from 1 minute to 1 hour.
18. The process of claim 9 , further comprising:
providing a second outer substrate;
depositing a second electrically conductive layer on the second outer substrate;
providing an anode layer;
providing an ion conductor layer; and
assembling an electrochromic device by arranging the treated lithium tungsten oxide cathodic electrochromic layer on one side of the ion conductor, the anode layer on the other side of the ion conductor, and the second electrically conductive layer on the side of the anode opposite to the ion conductor.