3D QLED Reflective Bank Electrode for Light Extraction Uniformity
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Solution Overview
Problem
Top emitting QLED displays face challenges with light extraction and voltage distribution due to insufficient conductivity of thin metal transparent conductive electrodes, leading to brightness variations across larger displays and angular dependence of color shift, which are exacerbated by the need for precise patterning and potential damage during wet etching processes.
Innovation Solution
A top emitting QLED apparatus with a reflective auxiliary electrode and a transparent filler material, where the auxiliary electrode is configured to reflect internally reflected light out of the sub-pixel and the transparent filler material aids in light extraction, while a patterned low refractive index layer helps in forming an internal reflection interface to enhance light directionality, and the reflective bank structure is designed to minimize crosstalk and current leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a thin metal transparent conductive electrode (15-20 nm Ag/Mg alloy) is used to enable high light transmission, then the emission area and color saturation are improved, but the conductivity is insufficient leading to voltage drop and brightness variation across larger displays
Solution Approach 1:
The patent divides the single transparent conductive electrode into two separate components: a thin transparent conductive electrode (15-20 nm Ag/Mg alloy) for light transmission and a separate auxiliary wire grid electrode for current distribution. This segmentation allows each component to perform its specialized function optimally without compromise.
Solution Approach 2:
The auxiliary wire grid electrode acts as an intermediary between the power supply and the thin transparent conductive electrode. It distributes current evenly across the display area before it reaches the emissive regions, preventing voltage drop and brightness variation while allowing the thin electrode to maintain high light transmission.
2Stability of the object's composition
If a nanoparticle transparent conductive electrode is used to remove the resonance cavity, then the angular dependence of color shift is reduced, but the conductivity remains insufficient for larger displays requiring an auxiliary electrode
Solution Approach 1:
The patent segments the light transmission function from the current conduction function. The nanoparticle transparent conductive electrode handles light transmission without creating a resonance cavity, while the separate auxiliary wire grid electrode handles current distribution, achieving both color consistency and sufficient conductivity.
Solution Approach 2:
The patent uses a composite electrode system combining nanoparticle transparent conductive material and wire grid structure. This composite approach leverages the optical properties of nanoparticles (no resonance cavity) and the electrical properties of the wire grid (high conductivity) to achieve both color consistency and reliable current distribution.
3Ease of manufacture
If a wet etch method is used for patterning the auxiliary electrode, then the manufacturing process is simplified, but the thinner areas on bank slopes are more porous and susceptible to etchant attack causing damage to QLED layers
Solution Approach 1:
The patent applies a protective coating to the bank slope areas before the wet etching process. This preliminary protective action prevents the etchant from attacking the porous thinner areas and damaging the QLED layers, while still allowing the wet etch method to be used for patterning the auxiliary electrode.
Solution Approach 2:
The protective coating acts as an intermediary barrier between the wet etchant and the vulnerable thin electrode areas on bank slopes. It allows the manufacturing process to proceed with wet etching while preventing harmful etchant attack on the QLED layers.
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 design improves light extraction efficiency, reduces brightness variations, and enhances color consistency across the display by effectively redirecting light to a narrower viewing angle, while also simplifying the patterning process and protecting the QLED layers from etchant damage.
Implementation Method 1
The auxiliary electrode reflects internally reflected light, including totally internally reflected light, out of the sub-pixel in a viewing direction
Implementation Method 2
The transparent low refractive index layer and the transparent filler material form an internal reflection interface for reflecting light onto the auxiliary electrode
Data Source
AI summary
A top emitting quantum dot light emitting diode (QLED) apparatus for an emissive display device sub-pixel, with at least one bank defining an emissive region of the emissive display device sub-pixel, includes an emissive layer deposited in the emissive region between a first electrode and a second electrode. The first electrode comprising a reflective metal, and the second electrode has a transparent conductive electrode and an auxiliary electrode. The bank has a sloped portion adjacent the emissive region. The auxiliary electrode includes a reflective conductive metal and is configured to cover the sloped portion, and the sloped portion is configured at an angle, such that the auxiliary electrode reflects internally reflected light out of the sub-pixel in a viewing direction and a first area of the transparent conductive electrode covering the sloped portion is thinner than a second area of the transparent conductive electrode in the emissive region.