Organic Light Emitting Device Blue Light Efficiency
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Solution Overview
Problem
Organic light emitting devices that emit white light have low light emitting efficiency, particularly due to low efficiency of blue light emission, which affects overall performance and increases driving voltage.
Innovation Solution
The device comprises multiple stacks emitting different colors, including a stack emitting blue light and a stack emitting mixed light of blue and yellow-green to red light, allowing blue light emission from two stacks to improve efficiency without increasing the number of stacks or driving voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple stacks emitting different colors are used to achieve white light emission, then color rendering is improved, but light emitting efficiency deteriorates due to low efficiency of blue light emission
Solution Approach 1:
The device divides the white light emission function into multiple independent stacks, each responsible for emitting a specific color component. The first stack emits blue light, the second stack emits yellow-green light, and the third stack emits red light. This segmentation allows each stack to be optimized for its specific wavelength range, improving overall light emitting efficiency while maintaining good color rendering.
2Loss of energy
If multiple stacks are added to improve white light emission efficiency, then light emitting efficiency is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple light-emitting stacks into a single integrated device structure with shared electrodes and encapsulation. The stacks are arranged in series between common anode and cathode electrodes, and are collectively encapsulated together. This merging approach improves light emitting efficiency through optimized charge distribution while avoiding the complexity increase that would result from completely separate devices.
3Loss of energy
If blue light emission efficiency is improved, then overall light emitting efficiency is improved, but driving voltage increases
Solution Approach 1:
Each stack is designed with locally optimized materials and structures tailored to its specific emission wavelength. The first stack uses materials optimized for blue light emission, the second for yellow-green, and the third for red. This local optimization allows each stack to achieve high efficiency at its designated wavelength while maintaining appropriate voltage characteristics, preventing overall driving voltage increase.
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 enhances light emitting efficiency, improves color viewing angle and white balance characteristics, and reduces the impact of red light on these aspects, resulting in improved picture quality without increasing the driving voltage.
Implementation Method 1
If the electrons generated in the cathode and the holes generated in the anode are injected into the organic light emitting portion, an exciton is generated by combination of the injected electrons and holes, and then the generated exciton is transited from the excited state to a ground state, whereby a light photon is emitted
Data Source
AI summary
Disclosed is an organic light emitting device comprising an anode; a cathode; and a plurality of stacks formed between the anode and the cathode. The plurality of stacks respectively emit their respective light of colors different from one another, wherein the plurality of stacks include a stack emitting blue light and a stack emitting mixed light of blue light and yellow-green to red light. Because the organic light emitting device includes a stack emitting blue light and a stack emitting mixed light of yellow-green to red light and blue light, blue light having a relatively low efficiency may be emitted from the two stacks, whereby overall light emitting efficiency is improved.