Stacked Quantum Dot Emissive Layers for High-Resolution QLED Patterning
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Solution Overview
Problem
Current methods for patterning quantum dot light-emitting devices (QLEDs) are limited by trade-offs between speed and resolution, with existing techniques being either fast but low-resolution or slow but high-resolution, and struggle to achieve single-colored emission from multilayer stacks.
Innovation Solution
The proposed solution involves a stacked arrangement of emissive layers with progressively narrower band gaps, where the narrowest band gap material is placed adjacent to the limiting charge transport layer, facilitating radiative recombination and minimizing photoluminescence from wider band gap layers, allowing for high-resolution patterning and single-colored emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional printing techniques are used for patterning QLEDs, then manufacturing speed is fast (>1 m2/s), but resolution is poor (>100 um pitch)
Solution Approach 1:
The patent divides the patterning process into multiple sequential steps: first forming a low-resolution pattern, then selectively removing portions, and finally forming additional emissive layers in specific regions. This segmentation allows each step to operate at optimal resolution without compromising overall manufacturing speed.
Solution Approach 2:
The patent performs preliminary patterning of the substrate with low-resolution structures before depositing high-resolution emissive layers. The preliminary patterns serve as templates that guide subsequent material deposition, enabling high-resolution final patterns to be formed faster than direct high-resolution patterning would allow.
2Adaptability or versatility
If multiple QD layers are stacked to achieve multicolor emission, then color variety is improved, but photoluminescence from wider band gap layers causes color purity to deteriorate
Solution Approach 1:
The patent creates different local structures for different color regions by selectively stacking QD layers only in specific areas. Each region has a tailored stack configuration where only the necessary QD layers are present, eliminating unwanted photoluminescence from layers that would emit incorrect colors in that particular region.
Solution Approach 2:
The patent removes wider band gap QD layers from specific regions where they would cause unwanted photoluminescence. By selectively extracting certain layers from the stack in specific device regions, the patent ensures that only the appropriate QD layers remain to emit the desired color without interference from other layers.
3Manufacturing precision
If layer-by-layer assembly method is used to stack different colored QDs, then patterning precision is improved, but manufacturing speed deteriorates (can only build one monolayer at a time)
Solution Approach 1:
The patent combines multiple QD layers into a single deposition step rather than assembling them sequentially. By merging the deposition of different colored QD layers into one coordinated process, the patent maintains the patterning precision of layer-by-layer assembly while achieving the manufacturing speed of simultaneous multi-layer formation.
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 enables the creation of high-resolution, multicolor displays with each region emitting substantially a single color, improving the efficiency and accuracy of light emission by controlling the recombination process and reducing unwanted photoluminescence.
Implementation Method 1
the emissive layer configured to emit light at a first wavelength upon radiative recombination of electrons and holes therein
Implementation Method 2
minimizing photoluminescence from wider band gap layers
Data Source
AI summary
A device includes a first light-emitting device and a second light-emitting device, each including an anode, a cathode, charge transport layers disposed between the anode and the cathode, and an emissive layer disposed between the charge transport layers. For the first light-emitting device, the emissive layer includes first quantum dots, the emissive layer configured to emit light at a first wavelength. For the second light-emitting device, the emissive layer includes emissive sub-layers provided in a stacked arrangement in a thickness direction. A first one of the emissive sub-layers includes the first quantum dots and is configured to emit light at the first wavelength, and a second one of the emissive sub-layers includes second quantum dots and is configured to emit light at a second wavelength different than the first wavelength.