Multilayer OLED Structure with Bipolar Charge Control
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Solution Overview
Problem
Organic light emitting devices with multi-stack structures face challenges of high driving voltage and short lifespan due to numerous interlayer boundaries, which hinder efficiency improvements.
Innovation Solution
Incorporating a multilayer-light emitting structure with at least two light emitting layers and a charge transport control layer, formed of a bipolar material or a mixture of hole and electron transport materials, to optimize charge transport between layers, reducing interlayer boundaries and lowering driving voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a multi-stack structure is used to improve efficiency, then the number of light emitting layers increases, but the number of interlayer boundaries increases, leading to high driving voltage and short lifespan
Solution Approach 1:
The patent merges multiple light emitting layers into a single stack structure, eliminating the need for multiple separate stacks. This reduces the number of interlayer boundaries while maintaining multiple light emitting layers within one integrated structure, thereby resolving the contradiction between improving efficiency and reducing device complexity
Solution Approach 2:
The patent segments the organic laminate into distinct functional regions including hole transport layer, multiple light emitting layers, electron transport layer, and charge transport control layers. This segmentation allows each layer to perform its specific function optimally while reducing the overall number of interlayer boundaries compared to multi-stack structures
2Productivity
If a multi-stack structure is used to increase the number of light emitting layers, then efficiency improves, but driving voltage increases and lifespan decreases
Solution Approach 1:
By merging multiple light emitting layers into a single stack with reduced interlayer boundaries, the patent decreases the overall number of interfaces where charge accumulation and defects can occur. This improves reliability and lifespan while maintaining the efficiency benefits of multiple light emitting layers
Solution Approach 2:
The patent introduces charge transport control layers as intermediary components between the multiple light emitting layers. These layers facilitate balanced charge transport and prevent charge accumulation at layer boundaries, thereby improving device reliability and lifespan without sacrificing the efficiency gains from multiple light emitting layers
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 efficiency, reduces driving voltage, and increases the lifespan of organic light emitting devices by ensuring uniform electron and hole transport to light emitting layers, thereby improving device performance.
Implementation Method 1
the organic light emitting device emits light based on driving current flowing between the first and second electrodes. The organic laminate includes a light emitting layer generating light through recombination of holes and electrons
Implementation Method 2
a charge transport control layer disposed on boundaries between the at least two light emitting layers. The charge transport control layer is a bipolar material transporting both electrons and holes and controlling an amount of charges transported at the boundaries
Data Source
AI summary
An organic light emitting device including a first electrode connected to a thin film transistor formed on a substrate, a second electrode opposite to the first electrode, and an organic laminate formed between the first electrode and the second electrode and including a hole transport layer, a multilayer-light emitting structure, and an electron transport layer. The multilayer-light emitting structure includes at least two light emitting layers emitting light of different colors through recombination of electrons and holes injected through the first and second electrodes, and a charge transport control layer formed of a bipolar material transporting both electrons and holes at boundaries between the at least two light emitting layers and controlling the amount of charges transported between the at least two light emitting layers.