Quantum Dot Emission Layer Ligand Gradient for Charge Injection Balance
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Solution Overview
Problem
The luminous efficiency of light-emitting elements containing quantum dots is limited by inefficient injection of electrons and holes into the light-emitting layer.
Innovation Solution
A light-emitting element structure is introduced, featuring an electron transport layer, a hole transport layer, and a light-emitting layer with quantum dots and ligands. The ligands have a lower concentration on the electron transport layer side compared to the hole transport layer side, facilitating efficient electron and hole injection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If quantum dots with uniform ligand distribution are used in the light-emitting layer, then the structural simplicity is maintained, but the luminous efficiency is limited due to inefficient charge carrier injection
Solution Approach 1:
The patent applies local quality by creating a light-emitting layer where ligand concentration varies spatially - specifically, the ligand concentration is lower near the electron transport layer interface and higher near the hole transport layer interface. This non-uniform distribution optimizes charge carrier injection locally at each interface while maintaining overall layer integrity, thereby improving luminous efficiency without requiring completely new device architectures.
2Productivity
If the ligand concentration is reduced on the electron transport layer side to improve electron injection, then the electron injection efficiency is improved, but the overall ligand distribution becomes non-uniform requiring complex control
Solution Approach 1:
The patent implements parameter changes by systematically varying the ligand concentration parameter across the light-emitting layer thickness. Specifically, the ligand concentration is tuned to be lower at the electron transport layer interface and higher at the hole transport layer interface. This controlled parameter variation optimizes charge carrier injection for both electron and hole types simultaneously, improving overall productivity while the gradient is achieved through controlled synthesis methods.
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 enhances the charge-carrier balance and improves the luminous efficiency of the light-emitting element by ensuring efficient injection and recombination of electrons and holes.
Implementation Method 1
ligands coordinated to the quantum dots, wherein the ligands in the light-emitting layer have a lower concentration on an electron transport layer side of the light-emitting layer than on a hole transport layer side of the light-emitting layer
Data Source
AI summary
A light-emitting element includes: an electron transport layer; a hole transport layer; and a light-emitting layer between the electron transport layer and the hole transport layer, the light-emitting layer including: quantum dots; and ligands coordinated to the quantum dots, wherein the ligands in the light-emitting layer have a lower concentration on an electron transport layer side of the light-emitting layer than on a hole transport layer side of the light-emitting layer.