OLED Encapsulation with Nanorod Optical Modulation Layers
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Solution Overview
Problem
Top-emission OLEDs suffer from a micro-cavity effect, leading to viewing-angle dependence issues due to changes in light-emitting spectra, which affects the device's efficiency and color purity.
Innovation Solution
An OLED encapsulating structure is developed with alternately formed barrier layers and optical modulation layers, where each optical modulation layer comprises a grid layer and a filler layer, with the grid layer made of a successively obliquely-grown nanorod thin film in a tri-layer structure of metal/dielectric/metal, and the dielectric comprising silicon dioxide or magnesium fluoride, to reduce viewing-angle dependence and enhance light-scattering emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If top-emission OLED structure is used to improve aperture ratio and device efficiency, then light emission from top is enhanced, but micro-cavity effect causes viewing-angle dependence and spectrum changes
Solution Approach 1:
The encapsulation structure is segmented into multiple functional layers: barrier layers for moisture protection and optical modulation layers for light control. Each layer performs a specific function, with the optical modulation layer further divided into grid sub-layers and filler sub-layers to independently address different optical issues.
Solution Approach 2:
Different regions of the encapsulation structure have different properties: the barrier layer provides dense moisture barrier properties, while the optical modulation layer with its grid and filler structure provides localized light scattering and cavity effect mitigation. The grid layer uses metal nanorods for specific optical modulation while the filler layer provides additional scattering.
2Reliability
If barrier layers are added to prevent moisture and oxygen penetration, then device lifespan is extended, but device structure complexity increases
Solution Approach 1:
The encapsulation structure integrates multiple functions into a unified system: the barrier layers provide both moisture protection and structural support, while the optical modulation layers simultaneously address viewing-angle dependence and provide additional optical enhancement. This multi-functional design avoids the need for separate independent systems for each function.
Solution Approach 2:
The encapsulation structure uses composite material systems combining organic and inorganic barrier layers with specific material compositions (e.g., ITO, ZnO, TiO2, SiO2, Alq3) to achieve both protection and optical modulation functions. The composite structure leverages the complementary properties of different materials.
3Reliability
If optical modulation layers with nanorod thin film are formed to reduce viewing-angle dependence, then light scattering is enhanced, but manufacturing process complexity increases
Solution Approach 1:
The patent replaces complex mechanical or lithographic patterning methods with a self-organizing chemical vapor deposition process that naturally forms the nanorod grid structure. The oblique angle deposition automatically creates the desired nanorod morphology and grid pattern through controlled material deposition, eliminating the need for complex mechanical fabrication steps.
Solution Approach 2:
The manufacturing process controls the deposition parameters (temperature, pressure, deposition rate, angle) to directly determine the nanorod dimensions, spacing, and orientation. By adjusting these parameters, the grid structure characteristics are tuned without changing the fundamental deposition method, simplifying the manufacturing approach.
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
The solution effectively reduces viewing-angle dependence and improves the contrast ratio of OLEDs by altering light propagation directions, while the barrier layers prevent moisture and oxygen penetration, thereby extending the device's lifespan and stability.
Implementation Method 1
the grid layer is formed of a successively obliquely-grown nanorod thin film... to reduce viewing-angle dependence and enhance light-scattering emission
Implementation Method 2
the barrier layers prevent moisture and oxygen penetration
Implementation Method 3
A top-emission OLED can improve device's efficiency, narrow spectrums and improve color-purity, but often suffers micro-cavity effect
Data Source
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AI summary
An OLED encapsulating structure and a manufacturing method thereof, and a light-emitting device are disclosed. The OLED encapsulating structure comprises: a base substrate (4), an OLED (1), barrier layers (2), and optical modulation layers (3); the OLED is formed on the base substrate; the barrier layers and the optical modulation layers are alternately and periodically formed on the OLED. The OLED encapsulating structure can reduce viewing-angle dependence of an OLED caused by a micro-cavity effect.