NiWTaO Counter Electrode Stack for Neutral Electrochromic Windows
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Solution Overview
Problem
Electrochromic devices, particularly electrochromic windows, face challenges in material stability over time, switching speed, and optical properties, with existing materials often exhibiting undesirable tinted states that are too blue and transparent states that are too yellow, limiting their commercial potential.
Innovation Solution
A novel electrochromic stack is developed using a cathodically coloring layer and an anodically coloring layer composed of nickel tungsten tantalum oxide (NiWTaO) with specific atomic ratios, which is formed through sputtering targets and can be deposited in direct physical contact without a separate ion conductor layer, offering improved stability and optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrochromic materials (tungsten oxide and nickel oxide) are used, then the basic electrochromic function is achieved, but material stability over time deteriorates and switching speed is slow
Solution Approach 1:
The patent applies composite materials by combining nickel oxide, tungsten oxide, and tantalum oxide in specific ratios to create a multi-component electrochromic material. This composite structure leverages the complementary properties of each oxide: nickel oxide provides anodic coloring, tungsten oxide provides cathodic coloring and stability, and tantalum oxide enhances overall material stability and switching performance, thereby resolving the contradiction between reliability and switching speed.
Solution Approach 2:
The patent applies parameter changes by precisely controlling the atomic ratios of the constituent oxides (Ni:WO3:Ta2O5 = 1:2:3 to 1:3:5) and deposition parameters (sputtering power, oxygen partial pressure, substrate temperature). By optimizing these parameters, the material achieves both high stability and fast switching speed, transforming the performance characteristics to simultaneously improve reliability and reduce switching time.
2Device complexity
If conventional electrochromic materials are used, then the device structure is simple, but optical properties deteriorate with tinted states too blue and transparent states too yellow
Solution Approach 1:
The patent applies parameter changes by adjusting the atomic ratios of nickel, tungsten, and tantalum oxides within specific ranges (Ni: 30-70 at%, WO3: 15-40 at%, Ta2O5: 10-30 at%). This compositional parameter optimization allows precise control over the optical properties, achieving neutral transparent states without excessive yellow tint and balanced tinted states without excessive blue color, while maintaining relatively simple device structure.
3Reliability
If a separate ion conductor layer is added between cathodically and anodically coloring layers, then ion transport is improved, but device complexity increases
Solution Approach 1:
The patent applies merging by combining the ion conductor functionality directly into the electrochromic active layer itself. The multi-oxide composition (nickel oxide, tungsten oxide, and tantalum oxide) serves dual functions: providing electrochromic coloring and facilitating ion transport. This eliminates the need for a separate ion conductor layer, maintaining device structural simplicity while ensuring efficient ion transport between the cathodically and anodically coloring regions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The novel electrochromic stack enhances material stability, switching speed, and optical properties, providing clearer tinted states and more neutral transparent states, thereby improving the commercial viability of electrochromic devices.
Implementation Method 1
The anodically coloring layer may be formed by sputtering one or more sputter targets to form the NiWTaO
Implementation Method 2
Electrochromism is a phenomenon in which a material exhibits a reversible electrochemically-mediated change in an optical property when placed in a different electronic state, typically by being subjected to a voltage change
Data Source
Figure 1A
Figure 1B~1C
Figure 1D~1F
AI summary
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 nickel tungsten tantalum oxide (NiWTaO). This material is particularly beneficial in that it is very transparent in its clear state.