Electrochromic device including capping layer
An electrochromic device includes an optically transparent first substrate, a first transparent conductor disposed on the first substrate, a counter electrode disposed on the first transparent conductor, an optically transparent, ionically conductive first capping layer disposed on the counter electrode, and configured to permit diffusion of alkali metal ions, and to block the diffusion of organic compounds and carbon, an optically transparent second substrate, a second transparent conductor disposed on the second substrate, a working electrode comprising electrochromic nanoparticles disposed on the second transparent conductor, and an electrolyte disposed between the first capping layer and the working electrode.
1. An electrochromic (EC) device comprising:
an optically transparent first substrate;
a first transparent conductor disposed on the first substrate;
a counter electrode disposed on the first transparent conductor;
an optically transparent, ionically conductive, first capping layer disposed on the counter electrode, and configured to permit diffusion of alkali metal ions, and to block diffusion of organic compounds and carbon;
an optically transparent second substrate;
a second transparent conductor disposed on the second substrate;
a working electrode comprising electrochromic nanoparticles disposed on the second transparent conductor; and
an electrolyte disposed between the first capping layer and the working electrode.
2. The EC device of claim 1 , wherein in the first capping layer is electrically conductive and comprises tantalum oxide, vanadium oxide, tungsten oxide, indium oxide, fluorine doped tin oxide, or mixtures thereof.
3. The EC device of claim 1 , wherein in the first capping layer is electrically insulating and comprises lithium niobate, silicon nitride, silicon dioxide, silicon oxynitride, aluminum oxide, lithium phosphorous oxynitride, lithium aluminum titanium phosphate, or mixtures thereof.
4. The EC device of claim 1 , wherein in the first capping layer has a thickness ranging from about 5 nm to about 1,000 nm, and the first capping layer has a porosity of less than 30%.
5. The EC device of claim 1 , wherein:
in the first capping layer has a thickness ranging from about 50 nm to about 100 nm; and
the porosity of the first capping layer ranges from about 1% to about 10%.
6. The EC device of claim 1 , further comprising an optically transparent and ionically conductive, second capping layer disposed between the working electrode and the electrolyte, and having a porosity of less than 30%, and configured to permit diffusion of alkali metal ions, and to block the diffusion of organic compounds and carbon.
7. The EC device of claim 1 , wherein a second capping layer is electrically conductive and comprises tantalum oxide, vanadium oxide, tungsten oxide, indium oxide, fluorine doped tin oxide or mixtures thereof.
8. The EC device of claim 1 , wherein a second capping layer is electrically insulating and comprises lithium niobate, silicon nitride, silicon dioxide, silicon oxynitride, aluminum oxide, lithium phosophorous oxynitride, lithium aluminum titanium phosphate, or mixtures thereof.
9. The EC device of claim 1 , wherein the working electrode further comprises a flux material configured to prevent or reduce sintering of the nanoparticles at a temperature of up to about 700° C.
10. The EC device of claim 9 , wherein:
the flux material forms a matrix in which the nanoparticles are disposed;
the flux material and the nanoparticles form a composite; or
the flux material forms shells around the nanoparticles.
11. The EC device of claim 9 , wherein the flux material comprises a lithium-rich anti-perovskite (LiRAP) material represented by the formula Li 3 OX, wherein X is F, Cl, Br, I, or any combination thereof.
12. The EC device of claim 1 , wherein:
the nanoparticles comprise WO 3-x , Cs x WO 3-x , or NbO x , where 0≤x≤0.33; and
the electrolyte comprises a gel electrolyte comprising polyurethane acrylate and a lithium salt.
13. The EC device of claim 1 , wherein the counter electrode comprises:
a passive layer disposed on the first capping layer and comprising passive nanoparticles and a flux material; and
a complementary layer disposed on the passive layer and comprising complementary nanoparticles and a matrix comprising a lithium metal oxide.
14. The EC device of claim 13 , wherein:
the complementary nanoparticles comprise NiO x where 1≤x≤1.5, Cr 2 O 3 , MnO 2 , FeO 2 , CoO 2 , RhO 2 , IrO 2 , or a combination thereof; and
the passive nanoparticles comprise CeO 2 nanoparticles and In 2 O 3 nanoparticles.
15. The EC device of claim 13 , wherein the complementary layer further comprises a flux material comprising a lithium-rich anti-perovskite (LiRAP) material represented by the formula Li 3 OX, wherein X is F, Cl, Br, I, or any combination thereof.
16. The EC device of claim 13 , wherein
the lithium metal oxide of the matrix comprises LiNbO 3 , Li 2 WO 4 , LiTaO 3 , or any combination thereof; and
the passive layer further comprises a matrix comprising LiNbO 3 , Li 2 WO 4 , LiTaO 3 , or any combination thereof.
17. A method of forming an electrochromic (EC) device, the method comprising:
forming a first transparent conductor on an optically transparent first substrate;
forming a counter electrode on the first transparent conductor;
forming an optically transparent, ionically conductive, first capping layer on the counter electrode, and configured to permit diffusion of alkali metal ions, and to block diffusion of organic compounds and carbon;
forming a second transparent conductor on an optically transparent second substrate;
forming a working electrode comprising electrochromic nanoparticles on the second transparent conductor; and
forming an electrolyte layer between the working electrode and the first capping layer.
18. The method of claim 17 , wherein:
the first capping layer is electrically conductive or electrically insulating;
the first capping layer is formed by solution deposition, chemical vapor deposition (CVD) or physical vapor deposition (PVD);
the first capping layer has a thickness ranging from about 5 nm to about 1000 nm; and
the first capping layer having a porosity of less than 30%.
19. The method of claim 17 , further comprising before the forming an electrolyte layer, forming an optically transparent, ionically conductive, second capping layer on the counter electrode, the second capping layer having a porosity of less than 30%, and configured to permit diffusion of alkali metal ions, and to block the diffusion of organic compounds and carbon.
20. The method of claim 1 , further comprising at least one of:
doping the counter electrode with Li ions before forming the first capping layer;
doping the working electrode with Li ions before forming a second capping layer; or
doping the counter electrode with Li ions before forming the first capping layer and doping the working electrode with Li ions before forming the second capping layer.
21. A method of operating the EC device of claim 1 , comprising performing at least 10,000 bright/dark cycles without forming organic residue on the counter electrode while permitting alkali ions to diffuse through the first capping layer between the counter electrode and the electrolyte.