Tandem White OLED Stacks with Charge Generation Layers
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Solution Overview
Problem
Tandem white OLED devices face challenges in controlling light emitting efficiencies among multiple color layers, leading to difficulties in achieving white light emission effectively.
Innovation Solution
The organic light emitting diode device comprises three stacks with specific light emitting layers and charge generation layers, including a blue light emitting layer, a lamination of green and yellow-green light emitting layers, and a lamination of blue and red light emitting layers, along with charge generation layers to enhance light emitting efficiency and driving voltage characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple light emitting layers emitting different colors are stacked to achieve white light emission, then the device can produce white light, but it becomes difficult to control light emitting efficiencies among different colors
Solution Approach 1:
The device is divided into multiple independent light emitting units (first, second, and third light-emitting units), each responsible for emitting specific color ranges. This segmentation allows independent control and optimization of light emitting efficiency for each color component, resolving the difficulty of controlling overall white light emission efficiency.
Solution Approach 2:
Each light emitting unit is designed with specific local characteristics - the first unit emits multiple peaks at wavelengths longer than 500nm (red-green-yellow range), while the second and third units emit at wavelengths shorter than 500nm (blue-cyan range). This local quality differentiation enables precise control over the spectral composition and efficiency of each color component in the white light output.
2Illumination intensity
If multiple light emitting layers are stacked to produce white light, then white light emission is achieved, but the light emitting efficiency needs to be improved
Solution Approach 1:
By segmenting the white light emission into multiple specialized light emitting units with non-overlapping wavelength ranges, each unit can be optimized for maximum efficiency at its specific wavelength range, reducing energy loss and improving overall light emitting efficiency.
Solution Approach 2:
Intermediate connectors are introduced between the light emitting units to facilitate efficient charge transport and energy transfer. These intermediaries ensure that electrical energy is effectively converted to light energy in each unit, minimizing energy loss and improving overall efficiency.
3Adaptability or versatility
If tandem structure with multiple light emitting layers is used, then device functionality is enhanced, but manufacturing complexity increases
Solution Approach 1:
The intermediate connectors serve multiple functions: they act as charge transport layers, provide structural support between layers, and enable electrical connection between light emitting units. This multi-functionality reduces the need for additional specialized components, simplifying the manufacturing process despite the tandem structure.
Solution Approach 2:
Multiple functional layers (charge transport, charge blocking, and structural support) are merged into the intermediate connectors, reducing the total number of separate deposition steps required. This combining of functions maintains device versatility while reducing manufacturing complexity.
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 the lifespan, light emitting efficiency, and driving voltage characteristics of the OLED device, ensuring effective white light emission and maintaining a secure viewing angle.
Implementation Method 1
a hole supplied from the first electrode is coupled with an electron received from the second electrode in the light emitting layer to form exciton, and a light is emitted by the energy generated while the exciton returns to the ground state
Data Source
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Figure 2
AI summary
A white organic light emitting diode device (10), comprising first (100) and second (380) electrodes facing each other above a substrate (50), first (160) and second (250) charge generation layers formed between the first electrode and the second electrode, a first stack (ST1) disposed between the first electrode and the first charge generation layer and including a first light emitting layer (140), a second stack (ST2) disposed between the first charge generation layer and the second charge generation layer and including a second light emitting layer (230), and a third stack (ST3) disposed between the second charge generation layer and the second electrode and including a third light emitting layer (330), wherein two of the first to third light emitting layers emit a blue light and the rest light emitting layer emits a yellow-green light.