Common Blue OLED Layer with Energy Barrier Dopants
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Solution Overview
Problem
In display apparatuses with organic electroluminescent elements, the efficient emission of different colors is hindered by electron leakage between light-emitting layers, and the use of electron block layers increases drive voltage, making it difficult to achieve efficient light emission without increasing production costs.
Innovation Solution
A display apparatus configuration where a common blue light-emitting layer is used, with red and green light-emitting layers disposed in contact with the cathode side of the blue layer, and formulated to satisfy specific energy level relationships between host and dopant materials to prevent electron conduction, allowing efficient emission without an electron block layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a common blue light-emitting layer is used for all pixels to reduce metal mask usage, then production cost decreases and manufacturing simplicity improves, but electron leakage occurs between layers causing inefficient light emission
Solution Approach 1:
The patent applies local quality by creating spatial variation in material composition within the light-emitting layers. The blue light-emitting layer contains a specific host material and dopant material with optimized concentrations in different regions. The red and green light-emitting layers have tailored compositions that differ from the blue layer, with specific dopant concentrations and host-guest ratios. This local compositional differentiation allows each layer to exhibit optimal electron transport and light emission properties for its specific function, preventing electron leakage while maintaining manufacturing efficiency.
2Reliability
If electron block layers are disposed between light-emitting layers to prevent electron leakage, then light emission efficiency improves, but drive voltage increases
Solution Approach 1:
The patent employs parameter changes by precisely controlling the energy level parameters of the host and dopant materials in each light-emitting layer. The HOMO and LUMO levels are engineered to create appropriate energy barriers between layers. Specifically, the blue light-emitting layer uses a host material with LUMO level at -2.1 eV and dopant material with LUMO level at -2.3 eV, while the red and green layers have different energy level configurations. This parameter optimization prevents electron leakage without requiring additional electron block layers, thereby avoiding voltage increase.
3Device complexity
If red and green light-emitting layers are stacked on the blue light-emitting layer, then device complexity is reduced and manufacturing is simplified, but electrons leak to the blue layer causing unwanted blue light emission
Solution Approach 1:
The patent utilizes composite materials by combining specific host materials and dopant materials in defined ratios within each light-emitting layer. The blue light-emitting layer comprises a host material (e.g., Alq3) and dopant material (e.g., BCP) with a specific weight ratio. The red and green light-emitting layers use different composite formulations with their own host-guest combinations and concentration ratios. These composite material configurations create distinct electronic properties for each layer, establishing energy barriers that prevent electron leakage from red/green layers to the blue layer, thereby eliminating unwanted blue light emission while maintaining structural simplicity.
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 enables efficient light emission of red and green layers while suppressing blue layer emission, reducing production costs and maintaining low drive voltage, thus improving luminous efficacy without the need for electron block layers.
Implementation Method 1
The organic electroluminescent element has a configuration in which an anode, a light-emitting layer containing an organic compound, and a cathode are stacked
Data Source
AI summary
A first light-emitting layer of a first organic electroluminescent element is disposed in common to a second organic electroluminescent element, a second light-emitting layer of the second organic electroluminescent element is disposed in contact with the first light-emitting layer and in the cathode side, and the first light-emitting layer is a light-emitting layer having an electron trapping property.