Organic EL Emitting Layer Layout for Chromaticity-Stable Efficiency
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Solution Overview
Problem
The use of pyrene compounds as host materials in layered emitting layers in organic electroluminescence devices leads to a chromaticity shift, reducing luminous efficiency due to increased emission wavelength and full width at half maximum, which weakens light interference.
Innovation Solution
An organic electroluminescence device with a specific arrangement of emitting layers and electrode types, utilizing different host materials and a thickness ratio between the layers, along with an optional color conversion portion, to enhance luminous efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pyrene compound is used as host material in layered emitting layers, then the device structure is simplified and manufacturing is easier, but emission wavelength becomes longer and full width at half maximum increases, causing chromaticity shift and reduced luminous efficiency
Solution Approach 1:
The emitting zone is divided into multiple emitting layers (first emitting layer with first host material, second emitting layer with second host material) instead of using a single pyrene-based emitting layer. This segmentation allows each layer to contribute differently to the overall emission, maintaining chromaticity while simplifying the overall device structure and manufacturing process.
Solution Approach 2:
Different host materials are used in different emitting layers to achieve local optimization of emission characteristics. The first host material and second host material are selected to have different properties, allowing each layer to emit at specific wavelengths that together produce the desired overall chromaticity, thereby maintaining high luminous efficiency.
2Device complexity
If pyrene compound is used as host material, then device fabrication is simplified, but light interference between emitting layers weakens, reducing luminous efficiency
Solution Approach 1:
The emitting zone is segmented into multiple distinct emitting layers with different host materials, which maintains device structure simplicity while enabling strong light interference effects through careful selection of layer thicknesses and material properties, thereby preserving high luminous efficiency.
Solution Approach 2:
The thickness ratio TCA/TAN between emitting layers is optimized to achieve constructive light interference. By controlling the film thickness parameters of each layer, strong interference effects are maintained despite the simplified device structure, thus improving luminous efficiency.
3Adaptability or versatility
If the thickness ratio TCA/TAN is outside the range of 0.3 to 1.5, then manufacturing flexibility is increased, but chromaticity shift occurs and luminous efficiency decreases
Solution Approach 1:
The thickness ratio TCA/TAN is optimized to be within the range of 0.3 to 1.5 to achieve constructive light interference between emitting layers. This parameter optimization ensures strong interference effects and maintains high luminous efficiency while still allowing manufacturing flexibility within the specified range.
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
Improves luminous efficiency by maintaining optimal light emission characteristics and reducing chromaticity shifts, thereby enhancing the performance of the organic electroluminescence device.
Implementation Method 1
When voltage is applied to an organic EL device, holes are injected from an anode and electrons are injected from a cathode into an emitting layer. The injected holes and electrons are recombined in the emitting layer to form excitons.
Implementation Method 2
the anode is a light reflective electrode having light reflectivity, and the cathode is a light transmissive electrode having light transmissivity
Implementation Method 3
in order to enhance the performance of the organic EL device, Patent Literature 3 describes a phenomenon in which a singlet exciton is generated by collision and fusion of two triplet excitons (hereinafter, occasionally referred to as a Triplet-Triplet Fusion (TTF) phenomenon)
Data Source
AI summary
In an organic EL device, an emitting zone includes a first emitting layer containing a first host material of formula (1) and a second emitting layer containing a different second host material. Ar1 in the formula (1) is a group of formula (11), (12), or (13). The thickness ratio TCA/TAN, where TCA is the film thickness of one of the first and second emitting layers disposed close to a cathode and TAN is the film thickness of the other emitting layer disposed close to an anode, ranges from 0.3 to 1.5. At least one of Configuration (i), where the anode is a light reflective electrode having light reflectivity and the cathode is a light transmissive electrode having light transmissivity; and Configuration (ii), where a color conversion portion is disposed on a side of the organic EL device through which light is extracted, is provided.