Electrochromic devices having optimized visual characteristics
The current invention describes an electrochromic panel having optimized visual properties. The properties have been optimized to provide an electrochromic panel having a very transparent clear state and a very black and opaque dark state. The coloration of the electrochromic panel has also been optimized to provide options for aesthetically pleasing windows. In one embodiment, the clear state comprises a CIE-Lab L* in transmission from 70 to 95, b* in transmission from −8 to 8, and a* in transmission from −4 to 4 and a dark state comprises a Tvis less than 0.01%, a CIE-Lab b* in transmission from −8 to 8, and a CIE-Lab a* in transmission from −8 to 8.
1. An electrochromic panel, comprising:
a first electrochromic device comprising a clear state and a dark state, wherein transition from the clear state to the dark state is controlled through application of a voltage to the electrochromic panel without application of Ultraviolet radiation and, wherein
the clear state comprises an L* value in transmission from 70 to 95, a b* value in transmission from −8 to 8, and an a* value in transmission from −4 to 4, wherein the L* value, the b* value, and the a* value are each defined according to the CIE-Lab color space.
2. The electrochromic panel of claim 1 , wherein the clear state comprises a visible transmittance (T vis ) from 70% to 80%.
3. The electrochromic panel of claim 1 , wherein the dark state comprises an L* value in transmission from 0 to 30, a b* value in transmission from −5 to −2, and an a* value in transmission from −7 to −5.
4. The electrochromic panel of claim 1 , further comprising a plurality of tinted states between the clear state and the dark state, wherein the plurality of tinted states are along a continuum of tints, and the panel has a delta E in transmission of less than 10 in the clear state, the dark state, and at all tinted states, across the panel in all dimensions, wherein delta E is a difference in color in the CIE-Lab color space, and is defined as:
Δ
E
=
(
L
2
*
-
L
1
*
)
2
+
(
a
2
*
-
a
1
*
)
2
+
(
b
2
*
-
b
1
*
)
2
.
5. The electrochromic panel of claim 4 , wherein the plurality of tinted states comprise a visible transmittance (T vis ) of between 0.01% and 80%.
6. The electrochromic panel of claim 4 , further comprising at least one gradient transparent conductive layer.
7. The electrochromic panel of claim 1 , further comprising at least one sequestration element.
8. The electrochromic panel of claim 3 , further comprising a sequestration element to maintain the clear state b* values in transmission and the clear state L* values in transmission over time.
9. The electrochromic panel of claim 1 , wherein the first electrochromic device is integrated into an insulated glass unit.
10. The electrochromic panel of claim 1 , wherein the first electrochromic device is integrated into an interior partition unit.
11. An electrochromic panel, comprising:
a first electrochromic device, the first electrochromic device comprising a first clear state and a first dark state, wherein transition from the first clear state to the first dark state is controlled through application of a voltage to the electrochromic panel without application of Ultraviolet radiation and;
a second electrochromic device laminated to the first electrochromic device such that incident light passes through both the first electrochromic device and the second electrochromic device, the second electrochromic device comprising a second clear state and a second dark state, wherein
the first clear state and the second clear state in combination comprise a visible transmittance (T vis ) greater than 55%, a b* value in transmission from −8 to 8, and an a* value in transmission from −5 to 5, wherein the b* value and the a* value are each defined according to the CIE-Lab color space.
12. The electrochromic panel of claim 11 , wherein the first dark state and the second dark state in combination comprise, a b* value in transmission from −8 to 8, and an a* value in transmission from −8 to 8.
13. The electrochromic panel of claim 12 , further comprising a plurality of tinted states between the first clear state and the first dark state, wherein the plurality of tinted states are along a continuum of tints, the panel has a delta E in transmission of less than 10 in the first clear state, the first dark state, and at all of the plurality of tinted states, across the panel in all dimensions, wherein delta E is a difference in color in the CIE-Lab color space, and is defined as:
Δ
E
=
(
L
2
*
-
L
1
*
)
2
+
(
a
2
*
-
a
1
*
)
2
+
(
b
2
*
-
b
1
*
)
2
.
14. The electrochromic panel of claim 13 , wherein the plurality of tinted states comprise a visible transmittance (T vis ) from 0.01% to 50%.
15. The electrochromic panel of claim 13 , further comprising an at least one gradient transparent conductive layer.
16. The electrochromic panel of claim 11 , further comprising at least one sequestration element.
17. The electrochromic panel of claim 12 , further comprising a sequestration element to maintain the first clear state and the first dark state b* values and the first clear state and the first dark state a* values over time.
18. The electrochromic panel of claim 12 , wherein the panel is integrated into an insulated glass unit.
19. The electrochromic panel of claim 12 , wherein the panel is integrated into an interior partition unit.
20. A method of operating an electrochromic panel, comprising:
switching between a dark state comprising a visible transmittance (T vis ) of less than 3% and a b* value in transmission from −8 to −8 and a clear state comprising a visible transmittance (T vis ) of greater than 55% and a b* value in transmission from −8 to 8, wherein the b* value and an a* value are each defined according to the CIE-Lab color space.
21. The method of claim 20 , further comprising:
switching between the dark state and a plurality of tinted states between the clear state and the dark state, wherein the plurality of tinted states are along a continuum of tints, wherein the tinted states have delta E in transmission less than 10, wherein delta E is a difference in color in the CIE-Lab color space, and is defined as:
Δ
E
=
(
L
2
*
-
L
1
*
)
2
+
(
a
2
*
-
a
1
*
)
2
+
(
b
2
*
-
b
1
*
)
2
.
22. The method of claim 20 , further comprising:
switching between the clear state and a plurality of tinted states between the clear state and the dark state, wherein the plurality of tinted states are along a continuum of tints, wherein the tinted states have delta E in transmission less than 10, wherein delta E is a difference in color in the CIE-Lab color space, and is defined as:
Δ
E
=
(
L
2
*
-
L
1
*
)
2
+
(
a
2
*
-
a
1
*
)
2
+
(
b
2
*
-
b
1
*
)
2
.
23. The method of claim 20 , wherein the switching comprises a switching speed between the clear state and the dark state, or between the dark state and the clear state, of less than 2 minutes.