Quantum Dot Electroluminescent Device Energy Level Transition Layer
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Solution Overview
Problem
In quantum dot electroluminescent devices, the large band shift between the hole transport layer material and the quantum dot luminescent material reduces the efficiency of hole injection and migration, leading to lower luminescence efficiency due to the significant difference in their highest occupied molecular orbital energy levels.
Innovation Solution
A quantum dot electroluminescent device structure is introduced, featuring a base material layer with a highest occupied molecular orbital energy level between that of the hole transport layer and the quantum dot luminescent material, acting as a transition layer to facilitate easier hole injection and migration, thereby improving luminescence efficiency. This structure includes a first electrode, an electron transport layer, a quantum dot luminescent layer with a base material layer and dispersed quantum dot luminescent material, and a second electrode, where the base material layer's energy level matches between the hole transport layer and the quantum dot luminescent material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a hole transport layer with HOMO energy level from 5.0 eV to 5.3 eV is used, then hole transporting ability is improved, but luminescence efficiency deteriorates due to large band shift with quantum dot material
Solution Approach 1:
The patent introduces an intermediate layer between the hole transport layer and quantum dot luminescent layer. This intermediate layer has a HOMO energy level (5.3-6.0 eV) that serves as a bridge, matching both the hole transport layer (5.0-5.3 eV) and quantum dot material (6.0-6.8 eV), thereby facilitating hole injection while maintaining luminescence efficiency
Solution Approach 2:
The patent modifies the energy level parameter of the transport layer by selecting materials with specific HOMO energy levels within the 5.3-6.0 eV range. This parameter optimization ensures better energy level alignment with both the hole transport layer and quantum dot material, resolving the band shift issue
2Loss of energy
If the HOMO energy level difference between hole transport layer and quantum dot material is reduced, then luminescence efficiency is improved, but hole transporting ability deteriorates
Solution Approach 1:
The intermediate layer acts as a mediator that decouples the energy level requirements. It maintains adequate HOMO energy level difference with the hole transport layer for efficient hole transport, while simultaneously reducing the energy level difference with the quantum dot material for improved luminescence efficiency
Solution Approach 2:
The patent applies different energy level characteristics to different layers: the hole transport layer maintains lower HOMO energy (5.0-5.3 eV) for efficient hole transport, while the intermediate layer has higher HOMO energy (5.3-6.0 eV) for better matching with quantum dot material, optimizing each layer's local function
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 enhances the efficiency of hole injection and migration, leading to improved luminescence efficiency in quantum dot electroluminescent devices by utilizing a base material layer as an energy level transition layer, specifically using organic or inorganic materials or their composites, and energy level transition materials like phosphate, thiol, or carboxylic acid compounds to optimize energy level alignment.
Implementation Method 1
quantum dot electroluminescent device
Implementation Method 2
a highest occupied molecular orbital energy level of the base material layer is between a highest occupied molecular orbital energy level of the hole transport layer and a highest occupied molecular orbital energy level of the quantum dot luminescent material
Data Source
AI summary
A quantum dot electroluminescent device and a display apparatus are provided. The quantum dot electroluminescent device includes: a first electrode, an electron transport layer, a quantum dot luminescent layer, a hole transport layer and a second electrode, wherein the quantum dot luminescent layer is disposed between the electron transport layer and the hole transport layer; the quantum dot luminescent layer includes a base material layer and a quantum dot luminescent material which is dispersed in the base material layer; a highest occupied molecular orbital energy level of the base material layer is between a highest occupied molecular orbital energy level of the hole transport layer and a highest occupied molecular orbital energy level of the quantum dot luminescent material.