Bismuth Hole-Injection Layer for OLED Voltage Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing OLEDs face challenges in achieving efficient hole-injection, leading to increased operating voltage, which affects the device's lifetime and efficiency.
Innovation Solution
A thin layer of a bismuth or gallium complex is used as a hole-injection layer in OLEDs, reducing the operating voltage while simplifying the fabrication process by requiring only one evaporation source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a p-dopant is used in the hole-transport layer to improve hole-injection, then hole-injection efficiency is improved, but the device complexity increases and manufacturing becomes more complex
Solution Approach 1:
The patent extracts the hole-injection function from the hole-transport layer by creating a separate dedicated hole-injection layer. This separates the hole-injection task from the hole-transport function, allowing each layer to be optimized independently. The hole-injection layer contains the p-dopant at high concentration (at least 90% by weight), while the hole-transport layer can be optimized for transport without excessive doping complexity.
Solution Approach 2:
The device is segmented into functionally distinct layers: a dedicated hole-injection layer separate from the hole-transport layer. This segmentation allows the hole-injection layer to specialize in hole injection using p-dopants like bismuth or gallium complexes, while the hole-transport layer focuses on charge transport, simplifying the overall device architecture and manufacturing process.
2Reliability
If the hole-injection layer thickness is increased to improve hole-injection, then hole-injection efficiency is improved, but the operating voltage increases
Solution Approach 1:
The patent optimizes the thickness parameter of the hole-injection layer to a specific range (0.5-5 nm) that balances hole-injection efficiency with operating voltage. This thin layer provides sufficient hole-injection capability through high p-dopant concentration while maintaining low resistance and minimizing the voltage required for operation.
Solution Approach 2:
The hole-injection layer has localized high p-dopant concentration (at least 90% by weight) specifically at the anode interface where hole injection is needed. This localized quality enhancement provides efficient hole injection without requiring the entire device structure to be thick or complex, thereby maintaining low operating voltage.
3Reliability
If a multi-component hole-injection layer is used to improve hole-injection, then hole-injection efficiency is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent extracts the hole-injection function into a separate dedicated layer with high p-dopant concentration, eliminating the need for complex multi-component mixtures in the hole-transport layer. This simplification allows for easier manufacturing while maintaining efficient hole injection through the specialized hole-injection layer.
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 use of a bismuth or gallium complex as a hole-injection layer efficiently lowers the operating voltage, thereby enhancing the lifetime and efficiency of OLEDs.
Implementation Method 1
a hole-injection layer arranged between the anode and the at least one hole-transport layer, where the at least one hole-injection layer comprises at least 90% by weight, based on the total weight of the hole-injection layer, of at least one bismuth or gallium complex
Implementation Method 2
the fabrication of the OLED, when the metal complex is deposited as a neat hole-injection layer via an evaporation process, is simplified
Data Source
AI summary
The present invention relates to an organic electroluminescent device comprising a hole-injection layer comprising a metal complex as a main component and a method for producing the organic electroluminescent device.