Organic EL Hole Injection Layer for Low-Voltage Durable Emission
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Solution Overview
Problem
Current organic electroluminescence (EL) elements face challenges in achieving low practical drive voltage, high light emission efficiency, and long lifetime due to inadequate hole injection/transport performance, electron blocking properties, and stability in thin film state.
Innovation Solution
Incorporating an arylamine compound doped with an electron acceptor in the hole injection layer and a pyrimidine derivative in the electron transport layer, combined with a blue light-emitting dopant, to enhance carrier balance and efficiency, while using an anthracene derivative as a host material in the light-emitting layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional hole transport materials (e.g., NPD, aromatic amine derivatives) are used, then hole transport ability is improved, but electron blocking property and heat resistance are insufficient
Solution Approach 1:
The patent uses composite materials by combining the arylamine compound (host material) with electron acceptor compounds (dopants such as F4-TCNQ, TCNQ, or I2) to create a doped hole transport layer. This composite structure provides both high hole mobility from the arylamine compound and superior electron blocking property and heat resistance from the electron acceptor dopant, resolving the contradiction between hole transport ability and reliability.
2Ease of operation
If drive voltage is reduced to improve ease of operation, then power consumption decreases, but light emission efficiency and durability are compromised
Solution Approach 1:
The patent changes the chemical and electrical parameters of the hole transport layer by introducing electron acceptor dopants. This alters the electrical conductivity and carrier concentration of the layer, enabling efficient charge transport at lower voltages while maintaining high light emission efficiency through optimized doping levels and material composition.
3Ease of manufacture
If materials with low heat resistance are used, then ease of manufacture is improved, but thermal decomposition occurs at low temperatures reducing durability
Solution Approach 1:
The patent changes the thermal stability parameter of the hole transport layer by incorporating electron acceptor compounds with high thermal resistance. These dopants raise the glass transition temperature and thermal decomposition point of the material system, enabling the element to maintain durability at operating temperatures while remaining manufacturable through standard vacuum deposition processes.
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 improves hole injection/transport efficiency, electron transport efficiency, and carrier balance, resulting in higher light emission efficiency and durability while maintaining a low drive voltage, thus addressing the limitations of existing organic EL elements.
Implementation Method 1
a hole injection layer, a hole transport layer... the hole transport material is important, and a hole transport material having a high hole injection property, a high mobility of holes
Implementation Method 2
improving the hole injection property, and the electron blocking property for blocking the electrons injected from the cathode to increase the possibility of recombination
Implementation Method 3
charges injected from both electrodes are recombined in the light-emitting layer to obtain light emission
Implementation Method 4
using an anthracene derivative as a host material in the light-emitting layer
Data Source
AI summary
According to the present invention, there is provided an organic electroluminescence element including at least an anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, and a cathode in the stated order, the organic electroluminescence element being characterized in that: the hole injection layer contains an arylamine compound represented by the following general formula (1) and an electron acceptor. The organic EL element of the present invention has a high light emission efficiency and an excellent durability, as compared with the related art, while maintaining the existing low drive voltage.