Tandem White OLED With Reflector And Segmented Units
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Solution Overview
Problem
Existing white OLEDs face challenges in achieving balanced and intense light emission across the red, green, and blue spectrums, leading to inefficiencies in power consumption and color reproduction, particularly in tandem structures which require high drive voltage and suffer from stability issues with blue light-emitting units.
Innovation Solution
A tandem white OLED device is designed with a spaced anode and cathode, incorporating a light reflector and two white light-emitting units with specific emission peak wavelengths, along with an intermediate connector to optimize emission spectra and reduce drive voltage, featuring a first unit with intense blue and yellow peaks and a second unit with intense blue, green, and red peaks, positioned relative to the reflector to enhance luminance efficiency and color gamut.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a tandem OLED structure is used to improve luminance efficiency and lifetime, then power efficiency and brightness are improved, but drive voltage increases proportionally to the number of stacked units
Solution Approach 1:
The device divides the white light emission function into two separate EL units, each optimized for specific spectral regions. The first unit emits blue and yellow light, while the second unit emits blue, green, and red light. This segmentation allows each unit to operate at optimized voltage levels rather than requiring a single unit to cover the entire spectrum, thereby improving power efficiency while managing drive voltage requirements
Solution Approach 2:
Each EL unit is designed with specific local quality characteristics - the first unit is optimized for blue and yellow emission with specific dopant concentrations, while the second unit is optimized for blue, green, and red emission. This local optimization of emission characteristics in different parts of the device enables improved overall power efficiency without requiring excessive drive voltage
2Illumination intensity
If blue light-emitting units are incorporated to achieve strong blue spectral component, then color gamut is improved, but stability and lifetime are reduced
Solution Approach 1:
The blue light emission function is segmented and distributed across two different EL units rather than relying on a single blue-emitting unit. The first unit provides blue emission with yellow emission, while the second unit provides blue emission along with green and red. This distribution reduces the operational burden on individual blue-emitting materials, thereby improving stability and lifetime while maintaining strong blue spectral intensity
Solution Approach 2:
Different operational parameters are applied to different EL units - the first unit operates with specific dopant concentrations and thickness optimized for blue-yellow emission, while the second unit operates with parameters optimized for blue-green-red emission. This parameter optimization for each unit improves the stability of blue light emission while maintaining the required spectral intensity
3Illumination intensity
If two light-emitting layers are used to improve color and luminance efficiency, then dopant concentration variability tolerance is higher, but achieving strong intensity in red, green, and blue portions simultaneously is difficult
Solution Approach 1:
The emission spectrum optimization problem is solved by segmenting the spectral coverage between two EL units. The first unit handles blue and yellow emission, while the second unit handles blue, green, and red emission. This segmentation allows each unit to be optimized for its specific spectral region without the complexity of optimizing all three primary colors in a single unit, thereby achieving strong intensity balance while managing device complexity
Solution Approach 2:
Each EL unit is designed with local quality optimized for its specific emission spectrum - the first unit has dopant concentrations and layer structures optimized for blue-yellow emission, while the second unit has parameters optimized for blue-green-red emission. This local optimization achieves strong overall spectral intensity balance while keeping the device structure manageable
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 results in improved power efficiency, higher brightness, and extended lifetime, while also enhancing the color gamut of OLED displays by optimizing the emission spectra and reducing drive voltage, thereby addressing the limitations of previous white OLED technologies.
Implementation Method 1
a light reflector associated with either the anode or the cathode
Implementation Method 2
an organic electroluminescent (EL) unit sandwiched between the anode and the cathode
Data Source
AI summary
A tandem white light-emitting OLED device is disclosed comprising a spaced anode and cathode, a light reflector associated with either the anode or the cathode, and at least two white light emitting units. The first white light-emitting unit has a set of at least two emission peaks in the blue and yellow spectral regions that are more intense than any other emission peaks that may be present in the emission spectrum of the first white light-emitting unit. The second white light-emitting unit is disposed closer to the reflector than the first white light-emitting unit and includes a set of at least three emission peaks in the blue, green, and red spectral regions that are more intense than any other emission peaks that may be present in the emission spectrum of the second white light-emitting unit. An intermediate connector is disposed between the first and second white light-emitting units.