QLED Light-Emitting Element with Dual-Ligand Function Regions
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Solution Overview
Problem
Conventional QLEDs suffer from brightness unevenness due to electric-field concentration and other factors, which has not been adequately addressed by existing configurations.
Innovation Solution
A light-emitting element with a function layer comprising a first function region with a functional material and a first ligand, and a second function region with the same functional material and a second ligand of higher volume resistivity, adjacent to the side surface of the first function region, is used to reduce brightness unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If insulating material is filled between quantum dots to improve carrier injection efficiency, then carrier injection efficiency is improved, but brightness unevenness remains due to electric-field concentration and coffee ring effect
Solution Approach 1:
The patent applies local quality by creating two distinct function regions with different ligand compositions and volume resistivities. The first function region uses a first ligand with lower volume resistivity to enhance carrier injection efficiency, while the second function region uses a second ligand with higher volume resistivity to suppress electric-field concentration and coffee ring effect at the periphery. This spatial differentiation of material properties resolves the contradiction between improving carrier injection and preventing brightness unevenness.
Solution Approach 2:
The light-emitting element is segmented into two function regions with distinct electrical characteristics. The first function region (central area) is optimized for carrier injection, while the second function region (peripheral area adjacent to side surfaces) is optimized for electric-field distribution. This segmentation allows each region to perform its specific function without interfering with the other, thereby resolving the brightness unevenness problem while maintaining high carrier injection efficiency.
2Reliability
If insulating material is filled between quantum dots, then voltage resistance is improved, but electric-field concentration and coffee ring effect cause brightness unevenness
Solution Approach 1:
Different ligand materials are selectively applied to different spatial regions: the first ligand in the central region provides adequate voltage resistance while maintaining good carrier injection, and the second ligand in the peripheral region provides higher volume resistivity to prevent edge effects. This local differentiation resolves the contradiction between voltage resistance and brightness uniformity.
Solution Approach 2:
The patent changes the volume resistivity parameter of the ligand material as a function of position. By using a first ligand with lower volume resistivity in the first function region and a second ligand with higher volume resistivity in the second function region, the patent optimizes both voltage resistance and electric-field distribution to eliminate brightness unevenness.
3Ease of manufacture
If uniform ligand distribution is used in the function layer, then manufacturing is simplified, but brightness unevenness occurs due to electric-field concentration at periphery
Solution Approach 1:
Instead of uniform ligand distribution, the patent implements local quality by using different ligands in different regions. The first ligand is used in the central first function region and the second ligand is used in the peripheral second function region. This approach maintains manufacturing feasibility through established deposition techniques while achieving uniform brightness by compensating for edge effects.
Solution Approach 2:
The patent uses a copying approach where the function layer is first formed with a uniform first ligand, and then the second ligand is selectively introduced to the peripheral region through controlled deposition or replacement processes. This allows the base structure to be manufactured simply while adding the corrective second ligand region to eliminate brightness unevenness.
Data Source
AI summary
A red light-emitting element according to the present disclosure includes a pixel electrode, a red light-emitting layer, and a common electrode in the stated order. The red light-emitting layer includes the following: a first red function region including red nanoparticles and first red ligands; and a second red function region including red nanoparticles and second red ligands different from the first red ligands, and being adjacent to at least a part of the side surface of the first red function region. The volume resistivity of the second red function region is higher than the volume resistivity of the first red function region.