Laminated Electrode Structure for Bidirectional OLED Viewability
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Solution Overview
Problem
Existing transparent organic electroluminescent display devices face challenges in achieving uniform light transmission and viewability from both sides due to a strong cavity effect, leading to poor rear surface viewability and high viewing angle dependence of chromaticity and luminance.
Innovation Solution
A display device structure with a laminated electrode configuration, including a transmissive first layer and a higher refractive index second layer, sandwiching an organic light-emitting layer, and an efficiency improving layer between the second and third electrodes, reduces the strong cavity effect and enhances light extraction efficiency to both front and rear surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a semi-transmissive metal film is used to ensure viewability, then front surface contrast is improved, but viewing angle dependence increases
Solution Approach 1:
The viewing experience is segmented into front and rear directions, with the front region optimized for high contrast using metal film, and the rear region optimized for wide viewing angles using transparent electrode, reducing overall viewing angle dependence
Solution Approach 2:
The front surface region employs a semi-transmissive metal film structure that provides high contrast at normal viewing angles, while the rear surface region uses a transparent electrode that maintains consistent optical properties across a wide viewing angle range
2Illumination intensity
If light-emitting regions are reduced in size to increase transmittance, then panel transmittance is improved, but display area decreases
Solution Approach 1:
The panel is segmented into light-emitting regions and transparent regions, with drive circuits positioned in the transparent region. This allows the light-emitting regions to maintain adequate size for display while the overall panel achieves high transmittance through the transparent electrode and transparent drive circuit area
Solution Approach 2:
The transparent electrode serves multiple functions: it acts as the rear electrode for bidirectional viewing, provides a transparent background that increases panel transmittance, and allows drive circuits to be positioned in transparent regions without compromising display quality
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 improves light transmission uniformity across visible wavelengths, reduces viewing angle dependence, and enhances viewability from both sides, while also simplifying the manufacturing process and reducing power consumption.
Implementation Method 1
An organic electroluminescent display device has been receiving attention as a promising candidate for a next-generation display device
Implementation Method 2
the first and third electrodes are each in a laminated structure including a first layer being transmissive, and a second layer being transmissive and having a refractive index higher than a refractive index of the first layer
Data Source
AI summary
A display device includes: a third electrode provided on a side of the second electrode opposite to the light-emitting layer; and an efficiency improving layer improving an efficiency of light extraction from the light-emitting layer, and the efficiency improving layer being provided between the second and third electrodes. The first and third electrodes are each in a laminated structure including a first layer being transmissive, and a second layer being transmissive and having a refractive index higher than a refractive index of the first layer.