Stacked Emissive Layer Hosts for OLED Viewing Angle and Lifespan
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Solution Overview
Problem
Conventional organic light-emitting devices suffer from degraded viewing angle characteristics and lifespan due to color recognition issues when viewed from different angles, leading to reduced color purity and shorter device lifespan.
Innovation Solution
The use of first and second emissive layers with hosts having different photoluminescence (PL) spectra, where the first emissive layer has a PL spectrum peak in a wavelength of 495-500 nm and the second emissive layer has a peak spaced 15-123 nm apart, with overlapping PL spectra to enhance viewing angle characteristics and lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single emissive layer with conventional host material is used, then the device structure is simple, but viewing angle characteristics are poor and color purity changes when viewed from different angles
Solution Approach 1:
The single emissive layer is segmented into multiple emissive layers (first emissive layer and second emissive layer), each containing different host materials with distinct photoluminescence characteristics. This segmentation allows each layer to contribute differently to the overall emission, improving viewing angle characteristics while maintaining color purity across different viewing angles.
Solution Approach 2:
Different regions (emissive layers) are assigned different host materials with specific photoluminescence properties tailored to their functional requirements. The first host material and second host material have different photoluminescence spectra that complement each other, creating local quality variations that enhance overall device performance for wide viewing angles.
2Ease of manufacture
If conventional host materials are used in the emissive layer, then the device is easy to manufacture, but lifespan is degraded
Solution Approach 1:
The emissive layer is constructed as a composite structure with multiple emissive layers containing different host materials. This composite approach combines the advantages of each host material, achieving both ease of manufacture through standard fabrication processes and enhanced lifespan through synergistic material properties that improve device stability and longevity.
3Reliability
If hosts with different photoluminescence spectra are layered to enhance viewing angle characteristics, then viewing angle performance improves, but device complexity increases
Solution Approach 1:
The emissive layer is divided into multiple segments (first emissive layer and second emissive layer), each with specific host materials optimized for particular photoluminescence characteristics. This segmentation enables improved viewing angle performance while managing complexity through a systematic layered structure.
Solution Approach 2:
The photoluminescence parameters (peak wavelengths, spectral shapes) of host materials are carefully selected and adjusted in each emissive layer. By changing these parameters systematically across layers, the invention achieves superior viewing angle characteristics while maintaining a manageable device structure.
4Ease of manufacture
If a single emissive layer is used, then the manufacturing process is simple, but color purity degrades when viewed from different angles
Solution Approach 1:
The emissive layer is segmented into multiple layers with different host materials, each contributing to specific color characteristics. This segmentation maintains color purity consistency across different viewing angles while using standard manufacturing processes for each layer.
Solution Approach 2:
Different emissive layers are assigned specific host materials with tailored photoluminescence properties to maintain color purity in different spatial regions and viewing directions. This local quality approach ensures consistent color performance across the display.
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 significantly improves viewing angle characteristics and extends the lifespan of organic light-emitting devices by maintaining color purity and reducing visual changes when viewed from different angles, while also enhancing luminance efficiency and driving voltage.
Implementation Method 1
the first emissive layer includes a first host of photoluminescence (PL) spectrum having a peak in a first wavelength, and the second emissive layer includes a second host of PL spectrum having a peak in a second wavelength spaced apart from the first wavelength by 15 nm to 123 nm
Data Source
AI summary
An organic light emitting device and an organic light emitting display device using the same are discussed, for changing a structure of an emissive layer to enhance viewing angle characteristics and lifespan. Emissive layers having hosts with different characteristics are stacked to prevent visual reduction depending on a viewing angle and to enhance a lifespan.