Nanoparticle Charge Transport Layer for Electron Injection in Displays
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Solution Overview
Problem
The combination of a light-emitting layer with a shallow conduction band lower end and an electron transport layer with small inorganic nanoparticles results in a large interface barrier, leading to degraded electron injection efficiency.
Innovation Solution
A light-emitting element with a charge transport layer comprising multiple layers of nanoparticles, where the particle size increases closer to the cathode, reducing the interlayer barrier and improving electron injection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a light-emitting layer with shallow conduction band lower end is combined with an electron transport layer containing inorganic nanoparticles with small particle size, then the light-emitting element can achieve efficient light emission, but the interface barrier between the cathode and electron transport layer becomes large, degrading electron injection efficiency
Solution Approach 1:
The electron transport layer is divided into multiple layers with different nanoparticle sizes. The first layer (closer to cathode) contains nanoparticles with a first average particle size, while the second layer (closer to light-emitting layer) contains nanoparticles with a second average particle size. This segmentation allows each layer to perform its specific function: the first layer facilitates electron injection from the cathode, while the second layer efficiently transports electrons to the light-emitting layer, thereby resolving the contradiction between maintaining low interface barrier and ensuring efficient electron transport.
Solution Approach 2:
Different regions of the electron transport layer are assigned different nanoparticle sizes tailored to their specific functional requirements. The region closer to the cathode uses nanoparticles with a first average particle size optimized for reducing the cathode interface barrier, while the region closer to the light-emitting layer uses nanoparticles with a second average particle size optimized for electron transport. This local differentiation of material properties allows simultaneous optimization of both electron injection and transport functions.
2Use of energy by moving object
If inorganic nanoparticles with small particle size are used in the electron transport layer, then the conduction band level can be adjusted, but the interface barrier with the cathode increases, reducing electron injection efficiency
Solution Approach 1:
The electron transport layer is segmented into multiple layers with different nanoparticle sizes. The first layer (closer to cathode) uses nanoparticles with a first average particle size that optimizes the interface barrier for electron injection, while the second layer (closer to light-emitting layer) uses nanoparticles with a second average particle size that optimizes conduction band level alignment for efficient electron transport. This segmentation allows independent optimization of both functions.
Solution Approach 2:
The average particle size of nanoparticles is used as a key parameter to control the conduction band level and interface barrier properties. By changing the nanoparticle size parameter between different layers, the patent achieves different electronic properties: smaller particles in the first layer reduce the cathode interface barrier, while larger particles in the second layer provide better conduction band alignment with the light-emitting layer, thus resolving the contradiction through parameter variation.
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
The improved charge transport layer design reduces the interlayer barrier, enhancing electron injection efficiency and overall performance of the light-emitting element.
Implementation Method 1
The first layer and the second layer include nanoparticles containing an identical semiconductor. A particle size of the nanoparticle of the second layer is larger than a particle size of the nanoparticle of the first layer.
Data Source
AI summary
A light-emitting element according to an aspect of the disclosure, comprising: a first electrode; a second electrode; a light-emitting layer disposed between the first electrode and the second electrode; and a charge transport layer disposed between the first electrode and the light-emitting layer. The charge transport layer includes a first layer and a second layer closer to the first electrode relative to the first laver. The first layer and the second layer include nanoparticles containing an identical semiconductor A particle size of the nanoparticle of the second layer is larger than a particle size of the nanoparticle of the first layer.