Non-light-emitting Variable Transmission Device Bus Bar Design
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Solution Overview
Problem
Non-light-emitting variable transmission devices face issues with electrical shorts and high leakage currents due to the migration of silver-containing ink through microscopic defects in underlying layers, which complicates the formation of bus bars without patterning the lower transparent conductive layer.
Innovation Solution
A non-light-emitting variable transmission device is formed with an electrochromic stack, a transparent conductive layer, an intermediate layer defining holes for bus bars that contact the upper transparent conductive layer, and a bus bar composed of conductive tape, allowing electrical connection without cutting the lower transparent conductive layer, using specific material selection and patterning techniques to prevent electrical shorts and high leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bus bar is formed by printing silver-containing ink directly on the upper transparent conductive layer, then electrical conductivity is improved, but the risk of electrical shorts and leakage currents increases due to ink migration through microscopic defects
Solution Approach 1:
The patent introduces an intermediate layer between the upper transparent conductive layer and the bus bar that acts as a barrier to prevent silver-containing ink from migrating through microscopic defects to the lower transparent conductive layer. This intermediary layer eliminates the harmful effect of ink migration while maintaining the electrical conductivity function of the bus bar.
Solution Approach 2:
The patent segments the bus bar structure into multiple functional layers: the upper transparent conductive layer, the intermediate barrier layer, and the silver-containing conductive layer. This segmentation isolates the potentially harmful silver ink from the sensitive lower conductive layer while preserving electrical functionality.
2Reliability
If the lower transparent conductive layer is patterned to prevent electrical shorts, then reliability is improved, but manufacturing complexity and process difficulty increase
Solution Approach 1:
Instead of patterning the lower transparent conductive layer, the patent uses an intermediate layer as a mediator that provides the necessary isolation function. This approach simplifies the manufacturing process by eliminating the complex patterning step while maintaining reliability through the barrier properties of the intermediate layer.
3Ease of manufacture
If the lower transparent conductive layer is not patterned to simplify manufacturing, then ease of manufacture is improved, but the risk of electrical shorts and high leakage currents increases due to ink migration
Solution Approach 1:
The intermediate layer serves as a mediator that enables the simplified manufacturing process (no patterning of lower conductive layer) while simultaneously providing the necessary electrical isolation. This single layer resolves both the manufacturing ease and reliability requirements.
Solution Approach 2:
The patent employs a composite structure combining the upper transparent conductive layer, the intermediate barrier layer, and the silver-containing conductive layer. This composite material approach integrates multiple functions (conductivity, isolation, and structural integrity) into a unified system that achieves both ease of manufacture and reliability.
Data Source
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AI summary
A non-light-emitting variable transmission device can include an active stack; a transparent conductive layer overlying the active stack; an antireflective layer overlying the transparent conductive layer and defining a hole; and a bus bar comprising a conductive tape that extends into the hole and contacts the transparent conductive layer. Proper selection of materials and design of a bus bar can allow an electrical connection to be made to the transparent conductive layer without the need to cut an underlying transparent conductive layer. A method of forming the non-light-emitting variable transmission device can include patterning the antireflective layer to define the hole that extends to the transparent conductive layer. Improved control in patterning allows the antireflective layer to be relatively thin and not remove too much of the underlying transparent conductive layer.