Angled Bus Bar Geometry 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 curtain effects, 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, providing symmetrical and rapid transition without overdriving, by configuring the bus bars to deliver current and voltage uniformly across the optically switchable device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bus bars are used to drive optically switchable devices, then the device can be switched between optical states, but non-uniform transition occurs due to high sheet resistance and terminal effects, causing hot spots and curtain effects
Solution Approach 1:
The bus bar is divided into multiple segments (first bus bar and second bus bar) positioned at different locations on the device. Each segment independently delivers current to different regions, breaking up the current path to reduce terminal effects and achieve more uniform transition across the device area.
Solution Approach 2:
The bus bars are configured with specific geometries (angled, L-shaped, or curved) that follow the device perimeter, creating non-uniform current distribution patterns that compensate for the natural non-uniformity caused by high sheet resistance. This local optimization ensures uniform overall transition.
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:
By segmenting the bus bar into multiple sections, the total current is distributed across multiple pathways. This allows fast switching to be achieved through coordinated current application to multiple segments rather than concentrating high current through a single path, preventing hot spot formation.
Solution Approach 2:
The patent applies current through multiple bus bars simultaneously or sequentially, using partial action on different device regions. This distributes the thermal load and prevents any single location from experiencing excessive current density that would cause hot spots.
3Reliability
If bus bars are positioned to minimize terminal effects, then uniform transition is achieved, but the device area required increases
Solution Approach 1:
The bus bars are configured in three-dimensional space with angled or L-shaped geometries that follow the device perimeter. This spatial arrangement allows current to be delivered uniformly across the device area without requiring additional planar space, as the bus bars utilize the vertical and angular dimensions rather than simply extending further in the plane.
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 switching between optical states, minimizing hot spots and curtain effects, ensuring consistent performance and reducing the risk of device damage.
Implementation Method 1
A first bus bar is affixed to the optically switchable device proximate to the corner and configured to deliver current and/or voltage for driving switching of the optically switchable device
Implementation Method 2
Electrochromism is a phenomenon in which a material exhibits a reversible electrochemically-mediated change in an optical property when placed in a different electronic state, typically by being subjected to a voltage change. The optical property being manipulated is typically one or more of color, transmittance, absorbance, and reflectance. 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.