Angled Bus Bar Layout for Uniform Electrochromic Switching
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Solution Overview
Problem
Existing electrochromic devices face issues with non-uniform transition between optical states due to high sheet resistance and terminal effects, leading to hot spots and the curtain effect, which can cause damage and slow switching rates.
Innovation Solution
The use of angled bus bars that follow the shape of the device's perimeter corners, allowing for symmetrical and rapid switching without overdriving, and are configured to minimize hot spots and uniformity issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional straight bus bars are used to deliver current to electrochromic devices, then the device structure is simple and easy to manufacture, but non-uniform current distribution occurs leading to hot spots and the curtain effect
Solution Approach 1:
The bus bar is designed with different geometries (angled, curved, or segmented configurations) in specific regions to locally optimize current distribution. The bus bar follows the contour of the device perimeter or includes angled segments that redirect current flow to high-resistance areas, creating non-uniform current density distribution where needed to compensate for terminal effects and achieve uniform optical transition across the device surface.
Solution Approach 2:
The bus bar configuration extends from a simple linear path into two-dimensional or three-dimensional geometries that follow the device perimeter contour. By adding spatial complexity in the form of angles, curves, or segments that wrap around device corners, the current distribution is optimized across the entire device surface, transforming the uniform current delivery approach into a spatially-varied delivery system.
2Speed
If high current is applied to achieve fast switching, then the transition speed increases, but hot spots are generated that can damage the device
Solution Approach 1:
The bus bar geometry is locally optimized to control current density distribution, directing higher current to regions with higher sheet resistance (typically corners and edges) while limiting current in regions that would generate excessive heat. This localized current management enables fast switching throughout the device without creating damaging hot spots in any specific region.
3Reliability
If the bus bar follows the perimeter shape including corners, then uniform current distribution is achieved reducing hot spots, but the bus bar length and complexity increase
Solution Approach 1:
The bus bar is divided into multiple segments or sections, each optimized for its local region of the device perimeter. Straight segments connect to angled or curved segments at device corners, allowing the bus bar to follow the perimeter contour without requiring a single continuous complex shape. This segmentation manages the total length while achieving the uniform current distribution goal.
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
Angled bus bars enable uniform and fast transitions between optical states, reducing the risk of device damage and minimizing the curtain effect, ensuring consistent performance across the entire electrochromic surface.
Implementation Method 1
Electrochromic materials may be incorporated into, for example, windows for home, commercial, and other uses. The color, transmittance, absorbance, and/or reflectance of such windows may be changed by inducing a change in the electrochromic material; i.e., electrochromic windows are windows that can be darkened or lightened electronically.
Implementation Method 2
One well known electrochromic material is tungsten oxide (WO3). Tungsten oxide is a cathodic electrochromic material in which a coloration transition, transparent to blue, occurs by electrochemical reduction.
Data Source
AI summary
This disclosure provides configurations, methods of use, and methods of fabrication for a bus bar of an optically switchable device. In one aspect, an apparatus includes a substrate and an optically switchable device disposed on a surface of the substrate. The optically switchable device has a perimeter with at least one corner including a first side, a second side, and a first vertex joining the first side and the second side. A first bus bar and a second bus bar are affixed to the optically switchable device and configured to deliver current and/or voltage for driving switching of the device. The first bus bar is proximate to the corner and includes a first arm and a second arm having a configuration that substantially follows the shape of the first side, the first vertex, and the second side of the corner.