Quantum-Dot Light-Emitting Element With Segmented Hole Transport
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Solution Overview
Problem
The inconsistency in ionization potential between the anode and the light-emitting layer inhibits efficient hole injection in existing light-emitting elements, as seen in configurations using p-type GaN quantum dots or p-type NiO thin films for the hole transport layer.
Innovation Solution
A light-emitting element with a hole transport layer comprising an n+-type semiconductor layer, a p+-type semiconductor layer, and a p-type semiconductor layer, where the n+-type and p+-type semiconductor layers are adjacent, and the p+-type and p-type semiconductor layers are adjacent, facilitating efficient hole injection into the light-emitting layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a p-type GaN quantum dot or p-type NiO thin film is used for the hole transport layer, then the device can be constructed with conductive inorganic substances, but the ionization potential is not consistent between the anode and the light-emitting layer, which inhibits hole injection efficiency
Solution Approach 1:
The hole transport layer is segmented into three distinct sub-layers with progressively optimized ionization potentials: a first hole transport layer adjacent to the anode, a second hole transport layer in the middle, and a third hole transport layer adjacent to the light-emitting layer. Each layer is designed with specific ionization potential characteristics to create a gradual energy level transition, solving the level mismatch problem through structural division.
Solution Approach 2:
Different regions of the hole transport layer are assigned different material compositions and ionization potential characteristics tailored to their specific functions. The first layer near the anode has one set of properties optimized for anode interface, while the third layer near the light-emitting layer has different properties optimized for quantum dot interface, with the middle layer providing transition. This local optimization resolves the global level matching issue.
2Speed
If conductive inorganic substances are used in the hole transport layer, then carrier mobility can be improved, but the ionization potential inconsistency creates energy barriers that reduce hole injection efficiency
Solution Approach 1:
The ionization potential parameter is systematically varied across the three hole transport layers. The first layer has a lower ionization potential suitable for anode interface, the second layer has intermediate ionization potential for transition, and the third layer has higher ionization potential matched to the light-emitting layer. This parameter gradient enables both high carrier mobility through inorganic materials and efficient hole injection through energy level alignment.
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 efficiency of hole injection into the light-emitting layer, enhancing the overall performance of the light-emitting element.
Implementation Method 1
the hole transport layer includes an n+-type semiconductor layer, and a p+-type semiconductor layer adjacent to the n+-type semiconductor layer and disposed closer to the light-emitting layer than the n+-type semiconductor layer
Data Source
AI summary
A light-emitting element according to the present invention includes an anode, a hole transport layer, and a light-emitting layer containing a quantum dot, and a cathode in this order, and the hole transport layer includes an n+-type semiconductor layer, and a p+-type semiconductor layer adjacent to the n+-type semiconductor layer and disposed closer to the light-emitting layer than the n+-type semiconductor layer.