Co-Sputtered Electrochromic Films for Neutral Color and Fast Switching
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Solution Overview
Problem
Conventional electrochromic materials have limited color range, primarily fixed tint colors like blue, which are uncomfortable for users and unsuitable for certain applications, and they suffer from short lifetimes and slow transitional times between colored and transparent states.
Innovation Solution
Development of electrochromic materials with a formula WO2.4-2.9:M1:M2:E1:E2:E3, achieved through magnetron sputtering and co-sputtering methods using carbide-based and graphite-based targets, allowing for extended color range including neutral colors like gray and brown, improved conductivity, and enhanced cycling stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional electrochromic materials are used, then the material structure is simple and manufacturing is easy, but the color range is limited and lifetimes are short
Solution Approach 1:
The patent uses composite materials by combining tungsten oxide with multiple dopants (molybdenum, niobium, tantalum) and co-dopants (nitrogen, carbon, silicon) to create a multi-component system. This composite approach enables extended color range including neutral colors like gray and brown, while improving cycling stability and lifetime through synergistic effects of the different elements.
Solution Approach 2:
The patent applies parameter changes by systematically varying the composition ratios of dopants and co-dopants, controlling deposition parameters during magnetron sputtering, and adjusting post-deposition annealing conditions. These parameter optimizations enable precise control over optical properties, conductivity, and structural characteristics to achieve neutral colors and improved performance.
2Use of energy by moving object
If thicker EC layers are deposited to improve performance, then the optical modulation is enhanced, but the ionic conductivity decreases and transitional time increases
Solution Approach 1:
The patent changes material parameters by incorporating dopants that increase ionic conductivity, enabling deposition of thicker EC layers (up to 10 μm) without dramatic performance drop. The dopants modify the material's ion transport properties, allowing thick layers to maintain both high optical modulation and adequate ionic conductivity.
Solution Approach 2:
The patent employs porous or nanostructured materials with controlled morphology that provide enhanced ion transport pathways. The specific surface area and pore structure are optimized to facilitate rapid ion diffusion even in thicker layers, maintaining fast transitional times while achieving superior optical modulation through increased material thickness.
3Speed
If conventional EC materials are used, then the manufacturing process is simple, but the transitional time between colored and transparent states is slow
Solution Approach 1:
The patent optimizes manufacturing parameters including magnetron sputtering power, gas flow rates, deposition temperature, and post-annealing conditions to control the material's crystalline structure, grain size, and defect density. These parameter optimizations enable faster ion diffusion and electron transport, resulting in rapid switching speeds while maintaining manufacturing feasibility.
Solution Approach 2:
The patent utilizes porous or nanostructured EC materials with high specific surface area and interconnected pore networks that facilitate rapid ion diffusion. The increased surface-to-volume ratio and shortened ion transport paths enable fast coloration and bleaching transitions, improving switching speed without requiring complex multi-step manufacturing processes.
4Adaptability or versatility
If dopants are added to enhance EC properties, then the color range and conductivity are improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent uses composite material formation through co-sputtering of multiple targets simultaneously, which inherently controls the relative dopant concentrations based on target composition and deposition parameters. This approach simplifies composition control compared to sequential doping, as the multi-element composite is deposited in a single process step with reproducible stoichiometry.
Solution Approach 2:
The patent optimizes deposition parameters including radio frequency power coupling, gas pressure, and target-to-substrate distance to achieve uniform dopant distribution and controlled composition. By carefully controlling these parameters, the patent achieves precise dopant incorporation with minimal variation, reducing manufacturing precision requirements while maintaining enhanced electrochromic properties.
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 materials exhibit increased electronic and ionic conductivity, longer lifetimes, and faster switching times between colored and transparent states, enabling the production of thicker EC layers with maintained performance, suitable for industrial and domestic applications, including smart glasses and energy storage devices.
Implementation Method 1
Magnetron sputtering and co-sputtering for producing EC materials may be performed by PDC method
Implementation Method 2
WO3 shows a strong reversible field-aided ion intercalation behavior. Ions such as Li+, Na+, K+, etc. may be easily introduced into the host WO3 matrix
Implementation Method 3
The electronic structure of WO3 is modified, and this strongly alters the optical properties of the material from transparent to a deep blue color
Data Source
AI summary
Inorganic electrochromic materials and methods of manufacturing utilize a reactive PDC magnetron, where co-sputtering synthesis of electrochromic materials are performed: (1) directly from carbide targets; (2) from relevant transition metals and graphite target, as well as non-metal elements such as Si, Ge, P, B, etc.; (3) directly from composite targets (fine powder mixture of transition metals, non-metal elements and graphite powder). Sputtering may be performed instantly from 1 to 4 targets. For co-sputtering, a combination of gas mixtures may be used: Ar/O2/N2, Ar/H2/N2/O2, Ar/NH3/O2, Ar/CO/N2/O2, Ar/CO/H2/N2/O2, Ar/CH4/N2/O2 and Ar/NH3/CO/N2/O2. This allows obtaining electrochromic materials with increased electronic and ionic conductivity, higher coloration and good cycling (lifetime). Moreover, different tints of blue as well as gray, black and brown colors neutral to the eye may be obtained. Sputtered electrochromic films were additionally improved by “thermo-splitting” pre-intercalated thin films. This allows achieving higher coloring and bleaching speed and better lifetime.