Quantum Dot Light-Emitting Element Carrier Balance
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Solution Overview
Problem
In light-emitting elements with quantum dots in the light-emitting layer, an excess of electrons often leads to a loss of carrier balance, causing electrons to flow out towards the anode electrode, which reduces luminous efficiency.
Innovation Solution
A light-emitting element is designed with a cathode electrode, an anode electrode, and two light-emitting layers with quantum dots having core-shell structures. The first quantum dot has a core with a higher conduction band level than the second quantum dot, preventing electron outflow and improving carrier balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If quantum dots are provided in a light-emitting layer, then light emission is achieved, but excess electrons are generated causing carrier balance loss and reduced luminous efficiency
Solution Approach 1:
The light-emitting layer is segmented into multiple layers, each containing quantum dots with specific conduction band levels. The first light-emitting layer has quantum dots with higher conduction band levels than the second light-emitting layer, creating a stepped energy landscape that prevents electron accumulation and maintains carrier balance, thereby improving luminous efficiency.
Solution Approach 2:
Different regions of the light-emitting layer are given different local properties through the use of quantum dots with varying conduction band levels. The first light-emitting layer (with higher conduction band level) and second light-emitting layer (with lower conduction band level) create localized energy barriers that control electron flow and prevent excess electron generation, maintaining carrier balance and improving overall luminous efficiency.
2Reliability
If electrons flow out from the light-emitting layer toward the anode electrode, then charge imbalance is reduced, but luminous efficiency is reduced
Solution Approach 1:
The patent introduces an intermediary structure with quantum dots having intermediate conduction band levels between the cathode and anode. This intermediary energy level structure acts as a barrier that prevents direct electron flow to the anode while maintaining carrier balance, thereby preserving luminous efficiency.
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 effectively suppresses electron outflow from the light-emitting layer to the anode electrode, enhancing luminous efficiency and maintaining improved performance in light-emitting devices.
Implementation Method 1
a level at a lower end of a conduction band of the first core is higher than a level at a lower end of a conduction band of the second core
Data Source
AI summary
A light-emitting element includes a first light-emitting layer including a first quantum dot and a second light-emitting layer including a second quantum dot provided between the cathode electrode and an anode electrode in order from the cathode electrode, the first quantum dot has a core-shell structure including a first core and a first shell, the second quantum dot has a core-shell structure including a second core and a second shell, and an energy level at a lower end of a conduction band of the first core is higher than an energy level at a lower end of a conduction band of the second core.