Quantum Dot Light-Emitting Element Charge Injection
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Solution Overview
Problem
The luminous efficiency of light-emitting elements containing semiconductor nanocrystals is limited by inefficient injection of electrons and holes into the light-emitting layer.
Innovation Solution
A light-emitting element structure is developed, featuring a quantum-dot layer with a stack of luminous first quantum dots and non-luminous second quantum dots, where the second quantum dots are more numerous on the electron transport layer side, enhancing efficient electron and hole injection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional light-emitting layer containing only luminous quantum dots is used, then the structure is simple, but the luminous efficiency is low due to inefficient electron and hole injection
Solution Approach 1:
The quantum-dot layer is segmented into two distinct functional regions: a first quantum-dot layer containing luminous quantum dots for light emission, and a second quantum-dot layer containing non-luminous quantum dots for efficient charge carrier injection and transport. This segmentation allows each layer to specialize in its function, resolving the contradiction between structural simplicity and luminous efficiency.
Solution Approach 2:
The non-luminous quantum dots in the second quantum-dot layer act as intermediaries that facilitate the injection and transport of electrons and holes into the luminous quantum dots. These intermediary particles enable efficient charge carrier management without directly participating in light emission, thereby improving luminous efficiency while maintaining reasonable structural complexity.
2Loss of energy
If non-luminous quantum dots are added to improve charge carrier injection, then luminous efficiency improves, but device complexity increases
Solution Approach 1:
The patent merges the functions of charge carrier injection and light emission into a single integrated quantum-dot layer structure. The first and second quantum-dot layers are combined in a stacked configuration where both layers work together synergistically - the non-luminous quantum dots support charge carrier management while the luminous quantum dots produce light, achieving functional integration that balances complexity and performance.
Solution Approach 2:
The quantum-dot layer structure exhibits multi-functionality: the second quantum-dot layer with non-luminous quantum dots performs charge carrier injection and transport functions, while the first quantum-dot layer with luminous quantum dots performs light emission. This multi-functional design allows a single integrated structure to handle multiple critical functions, reducing the need for separate components and thereby managing device complexity.
3Device complexity
If electrons and holes are not efficiently injected, then the device structure remains simple, but the charge-carrier balance is poor
Solution Approach 1:
The patent applies local quality by creating distinct regions with different quantum dot compositions and properties. The second quantum-dot layer contains non-luminous quantum dots specifically optimized for charge carrier injection and transport, while the first quantum-dot layer contains luminous quantum dots optimized for light emission. This local differentiation of material properties ensures efficient charge-carrier balance in the region where it is most critical, without requiring complex structures throughout the entire device.
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 configuration improves the luminous efficiency of the light-emitting element by ensuring efficient recombination of electrons and holes in the quantum-dot layer, thereby enhancing charge-carrier balance and light emission.
Implementation Method 1
a quantum-dot layer between the positive electrode and the negative electrode, the quantum-dot layer including a stack of a plurality of luminous, first quantum dots and a plurality of non-luminous, second quantum dots
Data Source
AI summary
A technique is provided that improves the efficiency of electron and hole injection in a light-emitting element containing quantum dots in a light-emitting layer thereof and hence improves the luminous efficiency thereof. The light-emitting element includes on a substrate: a positive electrode; a negative electrode; a quantum-dot layer between the positive electrode and the negative electrode, the quantum-dot layer including a stack of a plurality of luminous, first quantum dots and a plurality of non-luminous, second quantum dots; a hole transport layer between the positive electrode and the quantum-dot layer; and an electron transport layer between the negative electrode and the quantum-dot layer, the plurality of second quantum dots being more numerous in an electron transport layer side than in a hole transport layer side.