Organic Light Emitting Stack Structure for Color Temperature Stability
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Solution Overview
Problem
Illumination devices using organic light emitting elements face inefficiencies in wavelength efficiency due to differences among light emitting layers, particularly when current density changes during operation, affecting color temperature.
Innovation Solution
The illumination device employs a stack structure with independent light emitting layers for blue, green, and red emissions, where the blue layer has a lower efficiency and different energy bandgap, and the green and red layers have similar bandgaps, ensuring constant color temperature regardless of current density changes through co-deposition in the same light emitting layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple light emitting layers with different wavelengths are used to implement white light, then the illumination device can achieve white light emission, but there is a difference in efficiency among wavelengths according to time and change in current density
Solution Approach 1:
The device divides the light emitting structure into multiple independent stacks, each containing light emitting layers with specific wavelength ranges. The first stack contains blue light emitting layers (420-470 nm), the second stack contains green light emitting layers (500-590 nm), and the third stack contains red light emitting layers. This segmentation allows independent optimization and control of each wavelength range, resolving the efficiency inconsistency problem among different wavelengths.
Solution Approach 2:
Each stack is designed with specific local characteristics - the first stack has blue light emitting layers with particular dopant concentrations optimized for blue emission, the second stack has green light emitting layers optimized for green emission, and the third stack has red light emitting layers optimized for red emission. This local quality approach ensures that each wavelength range maintains consistent efficiency characteristics under varying current density conditions.
2Use of energy by moving object
If a conventional LED structure with inorganic semiconductor is used, then sufficient light efficiency can be achieved, but a lens and light emitting package are required which prevent slim device design
Solution Approach 1:
The invention extracts and removes the lens and light emitting package components from the conventional LED structure. By using organic light emitting elements that can be directly formed on a substrate through large-area coating, the patent eliminates the need for separate lens assemblies and protective packages, achieving slim device design while maintaining light efficiency.
Solution Approach 2:
The patent replaces the mechanical inorganic semiconductor LED structure with an organic light emitting element system. The organic layers are deposited directly on the substrate using coating techniques, substituting the traditional mechanical assembly of LED chips, lenses, and packages with a integrated organic thin-film structure that is inherently slim and flexible.
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 maintains consistent color temperature and enhances color rendering index, achieving white light emission with improved efficiency and flexibility in device design.
Implementation Method 1
An illumination device using an organic light emitting element is easily formed on a typical substrate as large-area coating thereof is possible. Particularly, the illumination device can be formed on a plastic substrate having flexibility, which is recently considered. In addition, the illumination device using an organic light emitting element is advantageous in that it may obtain high luminous efficacy and achieve low-voltage driving, a high response speed and a lightweight design.
Data Source
AI summary
The present disclosure relates to an illumination device which is realized by an organic light emitting element having a plurality of stacks and which achieves an improvement in relation to the efficiency difference among wavelengths by changing a light emitting layer structure of a predetermined stack.