OLED Electron Transport Layers Using Dipole-Optimized Compounds
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Solution Overview
Problem
There is a need to improve the performance of top emission and bottom emission OLEDs, particularly with respect to operating voltage and efficiency.
Innovation Solution
An organic light emitting device comprising a cathode, an anode, a light emitting layer, at least one first electron transport layer, and at least one second electron transport layer, where the first electron transport layer includes a compound of formula (I) and the second electron transport layer includes a compound of formula (II), both designed to enhance the performance by optimizing molecular dipole moments and layer configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional electron transport layers are used in OLEDs, then the device structure is simple, but the operating voltage is high and efficiency is low
Solution Approach 1:
The electron transport layer is divided into two distinct layers: a first electron transport layer containing compound (I) with low dipole moment adjacent to the emission layer, and a second electron transport layer containing compound (II) with high electron mobility adjacent to the cathode. This segmentation allows each layer to perform its specific function optimally, reducing overall operating voltage while maintaining structural organization.
Solution Approach 2:
Different regions of the electron transport system are assigned different material properties: the first layer uses compounds with low dipole moments (≤5 Debye) to minimize energy barriers at the emission layer interface, while the second layer uses compounds with high electron mobility to efficiently transport electrons to the emission layer, creating local optimization throughout the device.
2Productivity
If conventional electron transport layers are used in OLEDs, then the device structure is simple, but the external quantum efficiency is low
Solution Approach 1:
The electron transport function is segmented into two specialized layers that work together to maximize external quantum efficiency. The first layer with low dipole moment compounds ensures efficient electron injection from the emission layer, while the second layer with high mobility compounds ensures rapid electron transport to the cathode, minimizing losses and maximizing the number of electrons that contribute to light emission.
Solution Approach 2:
The invention changes key material parameters: selecting compounds with specifically controlled dipole moments (≤5 Debye for compound I) and high electron mobility (≥10^-5 cm²/Vs for compound II). These parameter optimizations in the respective layers directly improve electron transport efficiency and reduce energy losses, thereby increasing external quantum efficiency.
3Speed
If a single electron transport layer is used, then the device structure is simple, but the electron transport efficiency is insufficient
Solution Approach 1:
The electron transport pathway is divided into two functional segments: the first layer handles electron generation and initial transport from the emission layer with optimized dipole characteristics, while the second layer handles bulk electron transport to the cathode with optimized mobility characteristics. This segmentation enables high-speed electron transport throughout the device by matching material properties to functional requirements.
Solution Approach 2:
The electron transport system uses a composite structure of two different organic compounds with complementary properties: compound (I) with low dipole moment for interface optimization and compound (II) with high electron mobility for bulk transport. This composite approach creates synergistic effects that achieve superior electron transport efficiency compared to single-material systems.
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 use of these specific compounds in the electron transport layers significantly improves the operating voltage and efficiency of OLEDs, achieving high external quantum efficiency at low operating voltages.
Implementation Method 1
the compound of formula (I) has a molecular dipole moment of ≤ 5 Debye
Implementation Method 2
The holes and electrons mainly recombine in the EML to generate excitons. When the excitons drop from an excited state to a ground state, light is emitted.
Data Source
Figure 1
AI summary
The present invention relates to a organic light emitting device comprising a cathode, an anode, a light emitting layer, at least one first electron transport layer and at least one second electron transport layer, wherein the light emitting layer, the first electron transport layer and the second electron transport layer are arranged between the cathode and the anode, wherein the first electron transport layer comprises a compound of formula (I) L-M and the second electron transport layer comprises a compound of formula (II) as well as to a compound for use in an organic electronic device.