Light-Emitting Element With Hole-Blocking Layer
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Solution Overview
Problem
Current current excitation type light-emitting elements face challenges in achieving high luminous efficiency and long lifetime due to issues with material durability and carrier transport efficiency.
Innovation Solution
Incorporating a layer with a higher weight percentage of a hole-transporting organic compound and a hole-blocking material with a dipole moment of 2.0 debye or higher between the light-emitting layer and the electrode, controlling carrier transport to enhance luminous efficiency and extend the element's lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a hole-blocking layer is provided to improve light emission efficiency, then luminous efficiency is improved, but the lifetime of the light-emitting element becomes extremely short due to poor durability
Solution Approach 1:
The patent changes the material parameters of the hole-blocking layer by selecting organic compounds with specific properties (high ionization potential greater than 6.0 eV, high LUMO level greater than 2.0 eV, and high triplet energy greater than 2.7 eV). This parameter optimization allows the layer to block holes effectively while maintaining durability and achieving both high luminous efficiency and long lifetime.
Solution Approach 2:
The patent uses composite material strategies by combining the hole-blocking layer with other functional layers (hole-transporting layer, electron-transporting layer, light-emitting layer) to create a balanced device structure. The hole-blocking layer is composed of specific organic compounds (such as BCP, BPhen, or Alq3) that work synergistically with other layers to achieve both high efficiency and long operational lifetime.
2Ease of manufacture
If conventional materials are used in the light-emitting element, then manufacturing is simpler, but carrier transport efficiency is insufficient leading to lower performance
Solution Approach 1:
The patent optimizes carrier transport by selecting materials with specific parameter ranges: hole-transporting materials with HOMO level between 5.0-6.0 eV and hole mobility greater than 10^-6 cm²/Vs, electron-transporting materials with LUMO level between 2.0-3.0 eV and electron mobility greater than 10^-6 cm²/Vs. These parameter specifications enhance carrier transport efficiency while maintaining manufacturability through well-established deposition techniques.
3Device complexity
If the light-emitting element structure is simplified, then device complexity is reduced, but luminous efficiency and lifetime cannot be simultaneously optimized
Solution Approach 1:
The patent divides the light-emitting element into distinct functional segments: hole-injecting layer, hole-transporting layer, light-emitting layer, electron-transporting layer, and hole-blocking layer. Each segment performs a specific function, allowing independent optimization of material properties for each layer. This segmentation enables simultaneous achievement of high luminous efficiency and long lifetime without excessive overall complexity.
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 solution results in a light-emitting element with improved luminous efficiency and a longer lifetime, reducing power consumption and maintaining high performance over time.
Implementation Method 1
The first organic compound has a hole-transporting property
Implementation Method 2
the second organic compound is a substance into which a hole is not injected and which reduces a hole-transporting property of the first layer
Implementation Method 3
Light-emitting elements utilizing electroluminescence... By voltage application to this element, light emission can be obtained from the light-emissive substance
Data Source
AI summary
A light-emitting element disclosed in the present invention includes a light-emitting layer and a first layer between a first electrode and a second electrode, in which the first layer is provided between the light-emitting layer and the first electrode. The present invention is characterized by the device structure in which the first layer comprising a hole-transporting material is doped with a hole-blocking material or an organic compound having a large dipole moment. This structure allows the formation of a high performance light-emitting element with high luminous efficiency and long lifetime. The device structure of the present invention facilitates the control of the rate of the carrier transport, and thus, leads to the formation of a light-emitting element with a well-controlled carrier balance, which contributes to the excellent characteristics of the light-emitting element of the present invention.