Angled Bus Bar Geometry for Uniform Electrochromic Transitions
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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, allowing for 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 electrochromic 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 or zones along its length, with each segment independently controlled by separate voltage inputs. This segmentation allows different voltage levels to be applied to different regions of the electrochromic device, compensating for the voltage drops caused by high sheet resistance and preventing hot spots at terminal regions.
Solution Approach 2:
Different voltage levels are applied to different local regions of the bus bar based on their specific electrical characteristics. Regions with higher resistance receive higher voltages to maintain uniform current density throughout the device, ensuring uniform optical transition without hot spots or curtain effects.
2Productivity
If higher voltage is applied to speed up switching, then transition rate increases, but device damage risk increases due to overdriving
Solution Approach 1:
The voltage applied to the bus bar is dynamically adjusted based on real-time feedback from sensors monitoring the device's optical state and electrical parameters. The control system increases voltage during intermediate transition stages when higher current is needed for speed, then reduces voltage as the device approaches its target state, preventing overdriving and damage while maintaining fast switching.
3Speed
If voltage is applied to achieve fast transition, then switching rate improves, but non-uniform transition and hot spots occur
Solution Approach 1:
The bus bar is pre-configured with multiple voltage tap points and segmented zones before operation. During switching, voltage is applied simultaneously to multiple segments with appropriately differentiated levels, ensuring that all regions of the electrochromic device begin transitioning at the correct rate from the start, achieving both speed and uniformity without hot spots.
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
Enables uniform and fast switching between optical states, minimizing the risk of hot spots and curtain effects, ensuring consistent performance and reducing the risk of device damage.
Implementation Method 1
Tungsten oxide is a cathodic electrochromic material in which a coloration transition, transparent to blue, occurs by electrochemical reduction
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
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.