Organic EL Device Electron Transport Zone for TADF Efficiency
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Solution Overview
Problem
Current organic electroluminescence devices, particularly those using the TADF mechanism, face challenges in achieving high luminous efficiency due to differences in light emission mechanisms compared to traditional fluorescent devices, requiring a tailored structure design for TADF materials.
Innovation Solution
The organic electroluminescence device incorporates a blue pixel with a delayed fluorescent second compound and a fluorescent first compound emitting between 500 nm to 660 nm, along with a shared electron transporting zone and additional layers in the red, green, and blue pixels to enhance luminous efficiency and roll-off characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a conventional organic EL device structure is used with TADF materials, then the device can emit light through TADF mechanism, but the luminous efficiency is insufficient
Solution Approach 1:
The patent applies local quality by creating distinct electron transporting zones with different structures for red, green, and blue pixels. Each color pixel receives tailored electron transport characteristics through specific layer configurations (different number of layers, different materials, different thicknesses), optimizing the local electronic environment for each TADF emitter to maximize luminous efficiency while minimizing energy loss.
Solution Approach 2:
The patent employs parameter changes by systematically varying multiple parameters of the electron transporting zone including the number of layers, material composition, layer thickness, and HOMO/LUMO energy levels. These parameter optimizations are specifically tuned to match the characteristics of TADF materials, enabling efficient triplet exciton utilization and achieving high luminous efficiency.
2Use of energy by moving object
If the emitting layer thickness is increased to improve luminous efficiency, then more light can be emitted, but the roll-off value increases at high current densities
Solution Approach 1:
The patent applies dynamics by creating adaptable electron transporting zones that can dynamically adjust electron transport characteristics based on operating conditions. The multi-layer structure with varying HOMO/LUMO levels enables the system to optimize electron injection and transport efficiency across different current densities, maintaining stable performance and low roll-off values from low to high drive conditions.
3Device complexity
If a simplified single-layer electron transporting zone is used, then the device structure is simpler, but the luminous efficiency and roll-off characteristics are insufficient
Solution Approach 1:
The patent applies segmentation by dividing the electron transporting zone into multiple discrete layers with distinct functions. Each layer is optimized for specific electron transport tasks (electron injection, electron transport, energy level matching), creating a segmented architecture that achieves high luminous efficiency and optimal roll-off characteristics while maintaining manufacturing feasibility through modular layer construction.
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 luminous efficiency and reduces roll-off values, enabling high-efficiency light emission from the delayed fluorescent compound, particularly in the red pixel, and maintains performance across varying current densities.
Implementation Method 1
a first emitting layer between the anode and the cathode, the first emitting layer includes a delayed fluorescent second compound, and a fluorescent first compound emittable in a range from 500 nm to 660 nm
Implementation Method 2
an electron transporting zone interposed between the first emitting layer and the cathode and between the blue emitting layer and the cathode
Implementation Method 3
a hole transporting zone interposed between the first emitting layer and the anode and between the blue emitting layer and the anode
Implementation Method 4
An organic electroluminescence device (hereinafter, referred to as an organic EL device) includes an emitting layer between an anode and a cathode, where holes are injected from the anode and electrons are injected from the cathode into the emitting layer and the holes and the electrons are recombined to emit light
Data Source
AI summary
An organic electroluminescence device including: at least a first pixel and a blue pixel apposed on a substrate, in which the first pixel and the blue pixel each have an anode and a cathode, and the first pixel and the blue pixel have a first emitting layer and a blue emitting layer, respectively; a hole transporting zone provided between the first emitting layer and the anode and between the blue emitting layer and the anode; and an electron transporting zone provided between the first emitting layer and the cathode and between the blue emitting layer and the cathode, in which the first emitting layer includes a delayed fluorescent second compound and a fluorescent first compound capable of emitting light ranging from 500 nm to 660 nm, and the electron transporting zone includes: a first common layer; and an additional layer provided between the first emitting layer and the cathode.