Transparent Conductive Oxide Profiles for Flexible Electrochromic Devices
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Solution Overview
Problem
Electrochromic devices with flexible substrates face challenges such as non-uniform switching due to the 'iris effect' and manufacturing limitations, particularly with standard transparent conductive materials requiring high processing temperatures, leading to higher resistance and reduced transparency on flexible substrates.
Innovation Solution
The use of low-temperature transparent conductive layers with varying sheet resistance profiles, including conductive wires and nanowire meshes, and roll-to-roll processing to achieve uniform transmissivity across large areas, mitigating the iris effect and accommodating flexible substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard transparent conductive materials (TCOs) are used on flexible substrates, then electrical conductivity is improved, but processing temperature requirements cannot be met and resistance increases
Solution Approach 1:
The patent changes the processing temperature parameter from high (standard TCO processing) to low (below substrate melting point), enabling fabrication on flexible substrates while maintaining acceptable electrical conductivity through alternative material compositions and deposition methods
Solution Approach 2:
The patent employs composite transparent conductive structures combining multiple materials (e.g., metal oxides with conductive polymers, or layered TCO compositions) that achieve adequate electrical conductivity at low processing temperatures suitable for flexible substrates
2Ease of operation
If voltage is applied to electrochromic devices, then transmissivity switching is achieved, but non-uniform switching (iris effect) occurs due to voltage drop
Solution Approach 1:
The patent applies local quality by varying the sheet resistance of transparent conductive layers at different locations across the device - lower resistance near edges and higher resistance toward the center - to compensate for voltage drop and achieve uniform transmissivity switching across the entire device area
Solution Approach 2:
The patent implements dynamic resistance profiles where the electrical resistance distribution is optimized based on operational requirements, allowing the system to maintain uniform switching performance across different device sizes and operating conditions
3Illumination intensity
If high transparency is achieved with TCOs, then optical performance is improved, but electrical resistance increases on flexible substrates
Solution Approach 1:
The patent uses composite transparent conductive structures that combine materials with complementary properties - one component providing high optical transparency and another providing electrical conductivity - achieving a balance between transparency and low resistance suitable for flexible electrochromic devices
Solution Approach 2:
The patent optimizes multiple parameters simultaneously including layer thickness, material composition, and doping levels to achieve the optimal trade-off between optical transparency and electrical conductivity at low processing temperatures
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
This approach results in electrochromic devices with reduced or eliminated iris effects, achieving uniform switching and high transparency on flexible substrates, suitable for large-area applications.
Implementation Method 1
The stack includes a first transparent conductive layer, at least one electrochromic layer, a second transparent conductive layer... at least one of the first transparent conductive layer or the second transparent conductive layer has low resistance and high transmission
Implementation Method 2
Electrochromic devices, such as electrochromic windows or automotive electrochromic rearview mirrors, change transmissivity with application of voltage and current. The process relies on electrochemical redox (reduction, or gain of electrons and decrease in oxidation state, and oxidation, or loss of electrons and increase in oxidation state) reactions of a material
Implementation Method 3
The process relies on electrochemical redox (reduction, or gain of electrons and decrease in oxidation state, and oxidation, or loss of electrons and increase in oxidation state) reactions of a material, and is reversible
Data Source
AI summary
An electrochromic device is provided. The device includes a substrate and an electrochromic stack on the substrate. The stack includes a first set of bus bars, a first transparent conductive layer, at least one electrochromic layer, a second transparent conductive layer, and a second set of bus bars, wherein at least one of the first transparent conductive layer or the second transparent conductive layer includes resistivity that varies by horizontal location according to a resistivity profile. In some embodiments the resistivity profile has a vertical component that may or may not be in addition to the horizontal component. Various embodiments of these materials can be tuned as to profiles of vertical resistance and horizontal sheet resistance.