Electroluminescent Device Electron Transport Layer Leakage Current
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Solution Overview
Problem
Existing electroluminescent devices face challenges in minimizing leakage current, which affects their device characteristics and efficiency, particularly when using quantum dots as light emitting particles.
Innovation Solution
An electroluminescent device is designed with a specific structure including a first and second electrode, an emission layer with quantum dots, a hole transport layer, and an electron transport layer composed of at least two different organic semiconductor compounds, where the electron transport layer has a controlled surface roughness and mobility to minimize leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electron transport layer is made with conventional materials and structures, then the device structure is simple, but leakage current increases and device characteristics deteriorate
Solution Approach 1:
The electron transport layer is constructed as a composite structure comprising a first electron transport layer and a second electron transport layer with different material compositions and functions. The first layer (closer to emission layer) uses materials like Alq3 or BCP with specific LUMO levels for effective electron injection, while the second layer (closer to electrode) uses materials like TPBi or TCTA with different properties for electron transport and blocking. This composite approach reduces leakage current by creating optimized electron transport pathways and blocking holes effectively, while maintaining reasonable structural complexity.
Solution Approach 2:
Different regions of the electron transport layer are assigned different material properties and thicknesses to perform specific functions. The first electron transport layer near the emission layer is designed with specific thickness (5-20 nm) and material composition to facilitate electron injection, while the second layer is designed with different thickness (20-50 nm) and composition for electron transport and hole blocking. This local differentiation optimizes performance at each interface and reduces overall leakage current.
2Illumination intensity
If quantum dots are used as light emitting particles, then color purity and luminous efficiency are improved, but leakage current increases
Solution Approach 1:
The electron transport layer acts as an intermediary between the quantum dot emission layer and the electrode. It mediates charge transport by providing optimized electron pathways while blocking holes, preventing direct contact between holes and the electrode that would cause leakage. The specific material selection (Alq3, BCP, TPBi, TCTA) and thickness optimization create an intermediate zone that maintains the quantum dot emission performance while reducing leakage current through controlled charge transport.
3Speed
If the electron transport layer thickness is increased, then electron transport capability is improved, but surface roughness increases and leakage current worsens
Solution Approach 1:
The electron transport layer is segmented into two distinct layers with different thicknesses and material compositions. The first layer has smaller thickness (5-20 nm) to maintain surface smoothness and reduce roughness, while the second layer has larger thickness (20-50 nm) to provide sufficient electron transport capability. This segmentation allows each layer to be optimized independently - the first layer for surface quality and injection, the second for bulk transport - thereby achieving both smooth surface and high electron transport capability.
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 proposed structure effectively minimizes leakage current and enhances the device characteristics of electroluminescent devices, improving luminous efficiency and color purity by ensuring uniform charge transport and surface morphology.
Implementation Method 1
an electron transport layer disposed between the emission layer and the second electrode and including at least two different organic semiconductor compounds
Implementation Method 2
Quantum dots emit light when the excited electrons are transitioned from a conduction band to a valance band
Implementation Method 3
a first root-mean surface roughness of a surface of the electron transport layer obtained using a laser interferometer
Data Source
AI summary
An electroluminescent device and a display device including the same are provided. The electroluminescent device includes a first electrode and a second electrode facing each other; an emission layer disposed between the first electrode and the second electrode and including at least two light emitting particles; a hole transport layer disposed between the first electrode and the emission layer; and an electron transport layer disposed between the emission layer and the second electrode and including at least two different organic semiconductor compounds, wherein a first root-mean surface roughness of a surface of the electron transport layer obtained using a laser interferometer is in a range from about 0.5 nanometers to about 3 nanometers.