OLED Double-Layer Emission Zone Control
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Solution Overview
Problem
Existing organic light-emitting devices face challenges in achieving high efficiency and long lifespan due to limitations in hole and electron mobility, as well as exciton deterioration at the emission layer interfaces.
Innovation Solution
The implementation of a double-layered emission layer structure with specific host and dopant combinations, where the first emission layer has greater hole mobility and the second emission layer has greater electron mobility, and both have tailored triplet excitation energy levels to control the recombination zone and reduce exciton leakage, thereby enhancing luminescence efficiency and device lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-layer emission layer is used, then the device structure is simple, but the luminescence efficiency is low and lifespan is short due to poor carrier mobility balance and exciton deterioration at interfaces
Solution Approach 1:
The emission layer is divided into two distinct layers: a first emission layer with hole-transporting characteristics and a second emission layer with electron-transporting characteristics. This segmentation allows each layer to specialize in transporting one type of carrier, improving overall carrier mobility balance and reducing exciton deterioration at interfaces, thereby extending device lifespan while maintaining reasonable structural complexity.
Solution Approach 2:
Each emission layer is designed with specific local properties: the first emission layer has higher hole mobility and appropriate LUMO levels to block electrons, while the second emission layer has higher electron mobility and appropriate HOMO levels to block holes. This local quality optimization ensures efficient carrier transport within each layer while preventing carrier leakage, improving both reliability and luminescence efficiency.
2Device complexity
If carrier mobility is not optimized in the emission layer, then the device structure is simple, but luminescence efficiency is low due to poor carrier recombination
Solution Approach 1:
The emission layer is segmented into two functional layers with specialized carrier transport properties. The first emission layer optimizes hole transport with higher hole mobility, while the second emission layer optimizes electron transport with higher electron mobility. This segmentation enables efficient carrier recombination at the interface, significantly improving luminescence efficiency.
Solution Approach 2:
The patent optimizes key parameters including carrier mobility ratios (hole mobility > electron mobility in the first layer; electron mobility > hole mobility in the second layer), triplet energy levels (T1 ≥ 2.0 eV for the first host, 1.6-1.8 eV for the second host), and HOMO/LUMO energy levels. These parameter changes ensure balanced carrier injection and efficient recombination, maximizing luminescence efficiency.
3Device complexity
If exciton leakage is not controlled, then the device structure is simple, but the emission layer deteriorates quickly reducing device lifespan
Solution Approach 1:
The emission layer is segmented into two layers with complementary carrier transport characteristics. The first emission layer's electron-blocking property (higher hole mobility) and the second emission layer's hole-blocking property (higher electron mobility) create a confined recombination zone that prevents exciton leakage to adjacent layers, reducing deterioration and extending emission layer lifespan.
Solution Approach 2:
Each emission layer is designed with specific local quality properties: the first emission layer has optimized hole mobility and LUMO levels to block electrons, while the second emission layer has optimized electron mobility and HOMO levels to block holes. This local quality control creates effective barriers against exciton leakage, protecting the emission layers from deterioration.
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 luminescence efficiency by shifting the recombination zone and reducing exciton-induced deterioration, leading to a longer lifespan and higher performance of the organic light-emitting device.
Implementation Method 1
Holes provided from the first electrode may move toward the emission layer through the hole transport region, and electrons provided from the second electrode may move toward the emission layer through the electron transport region. Carriers (such as the holes and the electrons) may recombine in the emission layer to produce excitons. These excitons may transition from an excited state to the ground state to thereby generate light.
Implementation Method 2
the first host has a triplet excitation energy level (T1) value of 2.0 eV or more; and the second host has a T1 value of 1.6 eV or more and 1.8 eV or less
Data Source
AI summary
An organic light-emitting device and an electronic apparatus including the same are disclosed. The organic light-emitting device includes: a first electrode, a second electrode facing the first electrode; and an interlayer including a first emission layer and a second emission layer, which are located between the first electrode and the second electrode, wherein the first emission layer includes a first host and a first dopant, the second emission layer includes a second host and a second dopant, the first emission layer has greater hole mobility than electron mobility, the second emission layer has greater electron mobility than hole mobility, the first host has a triplet excitation energy level (T1) value of 2.0 eV or more, and the second host has a T1 value of 1.6 eV or more and 1.8 eV or less.