Electrochromic Bus Bar with Oxidation-Resistant Barrier
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Solution Overview
Problem
Electrochromic devices face challenges in achieving bus bars with low resistivity and good adhesion to underlying materials, limiting the selection of materials and processing conditions due to the risk of oxidizing the transparent conductive oxide layer during bus bar formation.
Innovation Solution
Incorporating an oxidation-resistant layer to protect the transparent conductive oxide layer during the formation of silver-based bus bars, allowing for higher firing temperatures and more aggressive firing conditions, which results in bus bars with lower resistivity and improved adhesion to the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If higher firing temperatures and more aggressive firing conditions are used to form bus bars, then resistivity and adhesion of bus bars are improved, but the transparent conductive oxide layer may be oxidized
Solution Approach 1:
An oxidation-resistant barrier layer is introduced as an intermediary between the transparent conductive oxide layer and the bus bar. This barrier layer prevents oxygen diffusion during high-temperature firing, allowing the use of aggressive firing conditions to achieve low resistivity and high adhesion bus bars without oxidizing the transparent conductive oxide layer.
Solution Approach 2:
The oxidation-resistant barrier layer creates an inert environment for the transparent conductive oxide layer during the firing process. By blocking oxygen transport, the barrier layer effectively creates a protected atmosphere that prevents oxidation even when fired at high temperatures in air or oxygen-containing environments.
2Object-affected harmful factors
If conventional firing conditions are used to form bus bars, then the transparent conductive oxide layer is protected from oxidation, but resistivity and adhesion of bus bars are compromised
Solution Approach 1:
The oxidation-resistant barrier layer acts as a mediator that decouples the firing process from the transparent conductive oxide layer. It allows high-temperature firing conditions to be applied to form low-resistivity, high-adhesion bus bars while simultaneously protecting the transparent conductive oxide layer from oxidation.
3Object-affected harmful factors
If materials and processing conditions are limited to protect the transparent conductive oxide layer, then oxidation is prevented, but selection of materials and processing conditions for bus bars is restricted
Solution Approach 1:
The oxidation-resistant barrier layer serves as a universal protective intermediary that enables the use of diverse bus bar materials and aggressive processing conditions. It broadens material selection for bus bars (including silver-based frits with various compositions) and processing conditions (higher firing temperatures, longer dwell times) while maintaining protection of the transparent conductive oxide layer.
Solution Approach 2:
The barrier layer enables significant changes in processing parameters including higher firing temperatures, extended firing times, and more aggressive atmospheric conditions. These parameter changes would otherwise be prohibited due to oxidation risk, but the barrier layer transforms the process window to allow optimized bus bar formation.
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 solution enables the use of a wider variety of silver-containing frits and firing conditions, achieving bus bars with resistivity as low as 8.0×10−6 Ω*cm and adhesion strength of at least 3 N to SiO2, enhancing the performance and reliability of electrochromic devices.
Implementation Method 1
Incorporating an oxidation-resistant layer to protect the transparent conductive oxide layer during the formation of silver-based bus bars
Implementation Method 2
firing the bus bar precursor to form a bus bar, wherein firing is performed such that the bus bar is at a temperature of at least 390° C.
Data Source
AI summary
An electrochromic device can include a substrate, a transparent conductive oxide layer over the substrate, and a bus bar over the substrate. The bus bar can include silver and has a resistivity of at most 6.7×10−6 Ω*cm, an average adhesion strength to SiO2 of at least 3N based on 20 measurements, as determined by Method A of ASTM B905-00 (Reapproved 2010), or a classification of at least 4, as determined by Method B of ASTM B905-00 (Reapproved 2010). In another aspect a process of forming an electrochromic device can include forming a transparent conductive oxide layer over a substrate; forming a bus bar precursor over the substrate, wherein the precursor includes silver; and firing the precursor to form a bus bar. Firing can be performed such that the first bus bar is at a temperature of at least 390° C.