Electrochromic Substrate Conductive Film High-Temperature Stability
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Solution Overview
Problem
Existing electrochromic dimmer elements face challenges in achieving stable electric conductivity after heating to 350 °C or higher due to the degradation of transparent conductive films, particularly ITO films, which experience increased electric resistance and reduced transparency.
Innovation Solution
A laminated substrate for electrochromic dimmer elements is developed, comprising a glass substrate with silicon oxide, aluminum oxide, boron oxide, and alkaline earth metal oxides, and a transparent conductive film with an indium oxide film and a tin oxide film containing tantalum, antimony, or fluorine, where the indium oxide film is directly formed on the glass substrate with a refractive index less than 0.4 and an extinction coefficient greater than 0.4, and a tin oxide film thickness greater than 35 nm, eliminating the need for a base layer and ensuring stable conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ITO films are used for transparent conductive films, then electric conductivity is excellent and transparency is maintained, but heat-resistance is poor and electric resistance increases after heating to 350°C or higher
Solution Approach 1:
The patent uses a composite transparent conductive film structure consisting of an ITO layer combined with a ZnO-based layer containing Ga, Al, or both as dopants. This composite structure allows the ITO to provide excellent electric conductivity and transparency while the ZnO-based layer provides heat resistance, preventing the electric resistance increase that occurs with pure ITO films after heating to 350°C or higher.
2Temperature
If SnO2-based films are used to improve heat-resistance, then stability at high temperature is achieved, but film thickness must be increased to decrease electric resistance, which degrades transparency
Solution Approach 1:
The patent combines ITO (which provides excellent conductivity at thin film thickness) with a ZnO-based layer containing Ga and/or Al (which provides heat resistance). This composite approach allows achieving both low electric resistance and high heat resistance without increasing film thickness, thereby maintaining transparency.
Solution Approach 2:
The patent optimizes the doping parameters of the ZnO-based layer by incorporating specific amounts of Ga and Al dopants. By controlling the dopant concentrations and the thickness of each layer, the patent achieves a balance between electric conductivity and heat resistance, allowing thin film formation that maintains both performance and transparency.
3Ease of manufacture
If transparent conductive films are heated to 350°C or higher during manufacturing, then processing is completed, but transparency and low resistance characteristics are degraded
Solution Approach 1:
The patent applies a protective ZnO-based layer containing Ga and/or Al dopants over the ITO layer before heating processing. This layer acts as a protective barrier that prevents oxygen from reaching the ITO layer during heating, thereby preventing the formation of oxygen holes and the subsequent increase in electric resistance and degradation of transparency that would otherwise occur during high-temperature manufacturing processes.
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 configuration provides stable and excellent electric conductivity after high-temperature processing, maintaining transparency and reducing sheet resistance, thus enabling increased dimmer element sizes and switching speeds.
Implementation Method 1
Electrochromic dimmer elements include electrochromic layers, in which a colored state and a transparent state switch to each other according to an application of an electric power
Data Source
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Figure 3
AI summary
A laminated substrate for an electrochromic dimmer element includes a glass substrate; and a transparent conductive film. The glass substrate includes a silicon oxide, an aluminum oxide, a boron oxide, an alkaline earth metal oxide, and an alkali metal oxide in a total amount of 90 mol% or more, and includes the alkali metal oxide in a total amount of 12 mol% or less. The transparent conductive film includes an indium oxide film containing tin, and a tin oxide film containing at least one of tantalum, antimony and fluorine, in this order from a glass substrate side. The indium oxide film is formed directly on the glass substrate, a refractive index and an extinction coefficient of the indium oxide film at a wavelength of 1.3 m is less than 0.4, and greater than 0.4, respectively. A film thickness of the tin oxide film is greater than 35 nm.