Organic Light Emitting Display Emission Layer Zone Segmentation
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Solution Overview
Problem
Organic light emitting display devices face reduced lifetime due to changes in carrier mobility with temperature, causing the recombination zone to deviate from the emission layer, which affects light emission and overall device performance, especially in varying temperature environments like those encountered in vehicles.
Innovation Solution
The device incorporates an emission layer with at least two zones, where the ratio of electron-type hosts is higher than hole-type hosts in one zone and equal to or higher in another, to maintain charge balance and prevent mobility-related deviations, ensuring consistent light emission across room and high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional emission layer with uniform host ratio is used, then the device structure is simple, but the recombination zone deviates from the emission layer at high temperature causing reduced lifetime
Solution Approach 1:
The emission layer is divided into multiple zones with different host material ratios. The first zone (near electron injection electrode) has a higher electron-type host ratio to accommodate increased electron mobility at high temperatures, while the second zone (near hole injection electrode) has a higher hole-type host ratio. This segmentation prevents recombination zone deviation and maintains stable light emission across temperature variations.
Solution Approach 2:
Different regions of the emission layer are assigned different host material compositions tailored to local requirements. The zone closer to the electron injection electrode receives more electron-type host material to counteract excessive electron mobility at high temperatures, while the opposite zone receives more hole-type host material. This local optimization ensures uniform charge distribution and stable recombination zone positioning throughout the emission layer.
2Reliability
If the host ratio in the emission layer is adjusted to maintain charge balance at high temperature, then lifetime is improved, but manufacturing precision requirements increase
Solution Approach 1:
The host material ratio parameter is varied across different zones of the emission layer. By changing the concentration and type of host materials in each zone, the invention optimizes charge carrier mobility balance at high temperatures. This parameter optimization ensures that the recombination zone remains stable and within the emission layer, thereby extending device lifetime under thermal stress.
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 enhances the lifetime of organic light emitting display devices by maintaining effective charge balance and light emission efficiency at both room and high temperatures, specifically relevant for applications in vehicles.
Implementation Method 1
An electron and a hole are injected from the two electrodes into the emission layer, and an exciton is generated by combining the electron with the hole. The organic light emitting devices are devices based on the principle that light is emitted when the generated exciton is dropped from an excited state to a ground state.
Data Source
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AI summary
Disclosed is an organic light emitting display device (200, 300) and lighting apparatus for vehicles using the same. The organic light emitting display device includes a first emission part (210, 310) between a first electrode (202, 302) and a second electrode (204, 304) and a second emission part (220, 320) on the first emission part (210, 310). The first emission part (210, 310) includes a first hole transport layer (212, 312), a first emission layer (214, 314), and a first electron transport layer (216, 316), and the second emission part (220, 320) includes a second hole transport layer (222, 322), a second emission layer (224, 324), and a second electron transport layer (226, 326). The second emission layer (224, 326) includes at least two zones (224a, 224b; 324a, 324b) including a hole-type host and an electron-type host, and a zone (224a, 324a) among the at least two zones (224a, 224b; 324a, 324b) closer to the first electrode (202, 302) than the second electrode (204, 304), a ratio of the electron-type host is higher than a ratio of the hole-type host in the zone.