OLED Hole Transport Zone HOMO Level Optimization
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Solution Overview
Problem
Conventional organic electroluminescent devices face challenges in achieving low driving voltage, high luminous efficiency, and long lifespan due to limitations in the hole transport zone when using fused azulene derivatives in the light-emitting layer, as the HOMO energy level of the hole transport zone affects both efficiency and voltage.
Innovation Solution
Incorporating a fused azulene derivative in the light-emitting layer and an arylamine derivative with a specific HOMO energy level in the hole transport zone, where the HOMO energy level of the arylamine derivative ranges from -5.0 eV to -4.65 eV, to optimize hole mobility and reduce driving voltage while maintaining high luminous efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the HOMO energy level of the hole transport zone is increased to reduce driving voltage, then driving voltage decreases, but luminous efficiency decreases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the HOMO energy level of the hole transport zone to fall within -5.0 eV to -4.65 eV. This specific parameter range resolves the contradiction by finding the optimal balance point where driving voltage is reduced while luminous efficiency is maintained at high levels, unlike conventional approaches that use broader or different energy level ranges.
Solution Approach 2:
The patent uses composite materials by combining the fused azulene derivative (compounds of formula 1) in the light-emitting layer with the arylamine derivative (compound of formula 2) in the hole transport zone. This composite structure allows the two materials to work synergistically, where the fused azulene derivative provides excellent hole and electron current properties while the arylamine derivative with specific HOMO energy level optimizes hole mobility, together resolving the voltage-efficiency contradiction.
2Productivity
If the HOMO energy level of the hole transport zone is decreased to increase luminous efficiency, then luminous efficiency increases, but driving voltage increases
Solution Approach 1:
The patent resolves this contradiction by establishing the HOMO energy level parameter within the specific range of -5.0 eV to -4.65 eV. This parameter optimization allows the system to achieve high luminous efficiency without the penalty of increased driving voltage, as the arylamine derivative's HOMO level is tuned to provide both efficient hole transport and favorable energy alignment with the light-emitting layer.
3Device complexity
If conventional hole transport zone materials are used with fused azulene derivative, then device structure is simple, but efficiency of light-emitting layer cannot be increased
Solution Approach 1:
The patent introduces a specific composite material system consisting of the fused azulene derivative (compounds of formula 1) in the light-emitting layer and the arylamine derivative (compound of formula 2) in the hole transport zone. This composite approach enables high efficiency in the light-emitting layer while maintaining reasonable device structure, as the two materials are specifically designed to work together with complementary properties.
Solution Approach 2:
The patent applies local quality by optimizing the hole transport zone with a material having specifically tailored properties (HOMO energy level of -5.0 eV to -4.65 eV) that are locally adapted to work with the fused azulene derivative in the light-emitting layer. This localized optimization of the hole transport zone's energy level profile enables efficient operation without requiring complex device architecture.
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 results in organic electroluminescent devices with lower driving voltage, higher luminous efficiency, and longer lifespan, as demonstrated by the production of OLED devices with improved performance metrics compared to comparative examples.
Implementation Method 1
a light-emitting layer between the first electrode and the second electrode, the light-emitting layer comprising a compound represented by formula (1)... A light-emitting layer comprising a phosphorescent dopant is preferable to have a light-emitting material having excellent hole and electron current properties
Implementation Method 2
a hole transport zone between the first electrode and the light-emitting layer... the hole transport zone comprises an arylamine derivative, and the HOMO energy level of the arylamine derivative satisfies the following equation (11)... in order to have a high hole mobility
Implementation Method 3
the azulene derivative comprised in the device of the present disclosure has a slow transition constant of the internal conversion of S2→S1, i.e. 7*10−8 s, the transition constant of the internal conversion of S1→S0 is fast, i.e. 7*10−12 s
Implementation Method 4
the intersystem crossing transition of S2→Tn transition is improved according to the conditions of the substitution material and the solvent polarity
Data Source
AI summary
The present disclosure relates to an organic electroluminescent device comprising a light-emitting layer and a hole transport zone. By comprising a specific combination of a light-emitting layer and a hole transport zone, it is possible to provide an organic electroluminescent device having low driving voltage, high luminous efficiency and/or long lifespan properties.