Electrochromic Device Ion Transfer Layer Fabrication
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Solution Overview
Problem
Existing electrochromic devices face challenges in achieving fast switching speeds between colored and bleached states with low voltage and maximizing self-bleaching time, while also requiring multiple vacuum processing cycles and thick adhesion layers that increase processing time.
Innovation Solution
A method of forming electrochromic devices in a vacuum processing chamber by sequentially depositing layers, including an electrode layer, a tungsten oxide precursor film, a lithium-nitride ion transfer layer, a lithium-fluoro-nitride electrolyte layer, and an ion storage layer, with ionized nitrogen used to enhance ion diffusion and reduce processing cycles, and a transparent polymer overcoat for environmental protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple vacuum processing cycles are used to deposit layers, then manufacturing precision is improved, but processing time increases
Solution Approach 1:
The patent combines multiple layer depositions (electrochromic layer, ion transfer layer, electrolyte layer, ion storage layer) into a single continuous vacuum processing cycle. The ion transfer layer is formed in-situ between the electrochromic and electrolyte layers without breaking vacuum, eliminating the need for separate processing cycles and reducing overall processing time while maintaining layer precision.
Solution Approach 2:
The ion transfer layer is formed preliminarily during the same vacuum cycle as the other layers, preparing the interface between electrochromic and electrolyte layers before final device assembly. This preliminary formation of the ion transfer layer with controlled thickness and composition ensures proper ion transport while avoiding additional processing cycles.
2Reliability
If thick adhesion layers are used to prevent flaking, then reliability is improved, but processing time increases
Solution Approach 1:
The patent applies adhesion promotion locally at the substrate-electrode interface rather than using thick adhesion layers throughout. The silicon monoxide and silicon dioxide layers are deposited only where needed for adhesion and brittleness prevention, with optimized thicknesses that provide sufficient mechanical support without excessive processing time.
Solution Approach 2:
The patent uses a composite adhesion system with silicon monoxide and silicon dioxide layers that work together to provide both adhesion promotion and mechanical support. This composite approach achieves reliable adhesion and prevents flaking with thinner total layer thickness compared to using a single thick adhesion layer.
3Speed
If ion transfer layer is formed to enhance ion transport, then switching speed is improved, but device complexity increases
Solution Approach 1:
The ion transfer layer formed from lithium nitride serves multiple functions simultaneously: it enhances ion transport between the electrochromic and electrolyte layers, provides interface protection, and establishes proper electrical contact. This multi-functional layer reduces the need for separate specialized layers, managing device complexity while improving switching speed.
Solution Approach 2:
The ion transfer layer acts as an intermediary between the electrochromic layer and electrolyte layer, facilitating efficient ion transport while protecting the interfaces from degradation. This intermediary layer with controlled thickness (2-5 nm) enables fast switching without requiring complex multi-layer structures.
4Speed
If ionized nitrogen is used during lithium deposition, then ion diffusion is enhanced, but processing complexity increases
Solution Approach 1:
The patent changes the deposition parameters by introducing ionized nitrogen during lithium deposition. This creates a reactive environment that enhances lithium diffusion into the tungsten oxide precursor and controls the formation of the lithium nitride ion transfer layer. The parameter change (adding ionized nitrogen) is integrated into the existing vacuum deposition process without requiring separate processing steps.
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
This approach reduces overall processing time, improves switching speed, and maintains optical and electrical performance with reduced degradation, allowing for faster and more efficient fabrication of electrochromic devices.
Implementation Method 1
This precursor film may comprise a metal oxide and is preferably tungsten oxide. In a subsequent step a mobile ion, which is preferably lithium, is deposited in the presence of ionized nitrogen. This forms the electrochromic layer, due to diffusion of the lithium into the tungsten oxide.
Implementation Method 2
a mobile ion, which is preferably lithium, is deposited in the presence of ionized nitrogen. This forms the electrochromic layer, due to diffusion of the lithium into the tungsten oxide. At the same time, it forms a thin lithium nitride ion transfer layer on the then exposed surface.
Data Source
AI summary
A method of preparing an electrochromic device involves forming multiple layers of selected materials on a substrate in a vacuum processing chamber. A first of these layers is an electrode layer deposited directly on the substrate and used for making contact to a subsequently deposited precursor film, preferably tungsten oxide, from which an electrochromic layer is formed by lithium loading in the presence of ionized nitrogen. This not only forms the electrochromic layer by diffusion of the lithium into the tungsten oxide, but also forms a thin lithium nitride ion transfer layer on the then exposed surface. Subsequently, a lithium fluoro-nitride electrolyte layer is formed on the ion transfer layer by evaporation from a lithium fluoride source in the presence of ionized nitrogen. An ion storage layer, which may be a vanadium oxide and a transparent second electrode layer are subsequently vacuum deposited.