OLED Micro-Cavity Structure for Light Extraction and Color Shift Reduction
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Solution Overview
Problem
Organic light emitting diode (OLED) display devices face challenges in optical efficiency and color shift when viewed from different angles due to internal total reflection and the wide emission wavelength band, which affects luminous efficiency and color purity.
Innovation Solution
The OLED display device incorporates a substrate with a thin film transistor, a first pixel electrode made of transparent conductive material, a second pixel electrode with a transflective metal layer, and a rough portion on the first pixel electrode, forming a micro-cavity structure with an opposing reflective electrode to enhance optical efficiency and reduce color shift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a distributed Bragg reflector (DBR) mirror is included to improve light extraction efficiency, then optical efficiency is improved, but device complexity increases
Solution Approach 1:
The patent extracts the light extraction function from the complex DBR mirror structure and implements it through a simplified micro-cavity structure consisting of a reflective electrode, organic emission layer, and pixel electrode with specific thickness ratios, eliminating the need for multi-layer DBR mirrors while maintaining high light extraction efficiency
Solution Approach 2:
The patent changes the structural parameters by defining specific thickness ratios (first thickness/second thickness between 0.3-0.7, third thickness/second thickness between 0.1-0.5) for the micro-cavity components, optimizing light extraction through parameter control rather than complex structural design
2Loss of energy
If a resonance structure is applied to control organic layer thickness for improving optical efficiency, then light extraction efficiency is improved, but color shift relative to viewing angle occurs
Solution Approach 1:
The patent applies local quality by creating a rough portion on the pixel electrode surface with specific roughness parameters (Ra: 5-50nm, Rq: 10-100nm) to enhance light extraction locally, while the overall micro-cavity structure maintains uniform optical properties to prevent color shift across different viewing angles
Solution Approach 2:
The patent introduces surface curvature through the rough portion on the pixel electrode, creating micro-scale curved surfaces that scatter and redirect light paths, improving extraction efficiency while the controlled curvature prevents the color shift issues associated with planar resonance structures
3Adaptability or versatility
If light is emitted in arbitrary direction by organic emission layer, then emission coverage is improved, but internal total reflection occurs reducing light extraction efficiency
Solution Approach 1:
The patent introduces the rough portion on the pixel electrode as an intermediary element between the organic emission layer and the external environment, facilitating light extraction by creating additional light-outgoing interfaces that mediate the transition from internal arbitrary-direction emission to external directed light output, reducing internal total reflection
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 micro-cavity structure improves optical efficiency and minimizes color shift on side surfaces, enhancing the overall performance of the OLED display device by optimizing light emission and transmission.
Implementation Method 1
a large number of photons emitted in an arbitrary direction may not reach an actual observer due to internal total reflection of an OLED, thereby lowering light extraction efficiency
Implementation Method 2
a large number of photons emitted in an arbitrary direction may not reach an actual observer due to internal total reflection of an OLED
Implementation Method 3
a rough portion on the first pixel electrode, a second pixel electrode on the rough portion and having a rough pattern
Data Source
AI summary
An organic light emitting diode (OLED) display device and a method of manufacturing the same. The device includes a substrate, a thin film transistor (TFT) on the substrate and including an active layer, a gate electrode, a source electrode, and a drain electrode, a first pixel electrode coupled to one of the source and drain electrodes, a rough portion on the first pixel electrode, a second pixel electrode on the rough portion and having a rough pattern, an intermediate layer on the second pixel electrode including an organic emission layer (EML), and an opposing electrode on the intermediate layer.