Polysiloxane Charge Control Layer for OLED Efficiency
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Solution Overview
Problem
Current OLED and QLED technologies face limitations in charge mobility and out-coupling efficiency, leading to reduced luminous efficiency and shorter lifespan due to thermal degradation and surface defects, as well as unbalanced charge injection and reduced color gamut.
Innovation Solution
A light emitting diode (LED) is designed with a charge control layer made of polysiloxane-based material chemically bonded to a charge transfer layer, enhancing charge balance and out-coupling efficiency by improving the stability of the electron transport layer and reducing surface defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If current densities are increased or driving voltages are raised to improve luminance in OLED, then luminance is improved, but luminous life time becomes shorter due to thermal degradation and deteriorations of organic materials
Solution Approach 1:
The patent introduces a charge control layer as an intermediary between the charge transfer layer and the emitting material layer. This layer mediates charge injection by providing balanced electron and hole injection capabilities, reducing the need for high current densities or driving voltages, thereby improving luminance while extending device lifetime through reduced thermal degradation
Solution Approach 2:
The patent changes the chemical composition parameter by using polysiloxane-based materials with specific functional groups in the charge control layer. This parameter change enables balanced charge injection and improved charge mobility, allowing operation at lower current densities and voltages, thus improving both luminance efficiency and device stability over time
2Ease of manufacture
If surface defects are present at interfaces between emissive layers, then manufacturing is simplified, but luminous efficiency is reduced and device reliability deteriorates
Solution Approach 1:
The charge control layer serves as an intermediary layer that chemically bonds to the charge transfer layer and provides a defect-free interface with the emitting material layer. This intermediary layer eliminates surface defects at the interface, improving charge injection efficiency and device reliability while maintaining ease of manufacture through solution processing
Solution Approach 2:
The patent uses composite material structure combining polysiloxane-based charge control layer with charge transfer layer and emitting material layer. This composite structure provides both manufacturing simplicity through solution processing and high reliability through defect-free interfaces and balanced charge injection
3Device complexity
If charge un-balancing occurs due to relative mobility difference between holes and electrons, then device structure is simplified, but luminous efficiency is reduced
Solution Approach 1:
The charge control layer acts as an intermediary that balances charge injection by providing both electron injection capability (through LUMO level alignment) and hole injection capability (through HOMO level alignment). This mediates the mobility difference between electrons and holes, achieving balanced charge injection without increasing device structural complexity
Solution Approach 2:
The charge control layer performs multiple functions simultaneously: it provides balanced charge injection for both electrons and holes, improves charge mobility, and ensures stable operation. This multi-functionality resolves charge un-balancing issues without requiring separate complex charge transport pathways, maintaining simple device structure while improving luminous efficiency
4Device complexity
If light is emitted toward other directions rather than intended emitting direction, then device structure is simplified, but out-coupling efficiency is reduced
Solution Approach 1:
The patent changes the optical parameter by using materials with specific refractive indices in the charge control layer and charge transfer layer. This refractive index optimization directs light emission toward the intended direction, improving out-coupling efficiency without requiring complex light extraction structures, thus maintaining simple device architecture
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 solution results in improved luminous efficiency, extended lifespan, and balanced charge injection, enhancing the overall performance of the LED and enabling compliance with high color gamut standards like ITU-R Recommendation BT.2020.
Implementation Method 1
a charge control layer, wherein the charge control layer includes a polysiloxane-based material bonded chemically to a surface of the charge transfer layer
Implementation Method 2
an inorganic emitting material layer disposed between the first and second electrodes
Data Source
AI summary
The present disclosure relates to a light emitting diode that includes a charge control layer disposed between a charge transfer layer and one electrode and including polysiloxane-based material chemically bonded to a surface of the charge transfer layer and a light emitting device having the same. The charge control layer is configured to remove a surface defect of the charge transfer layer, to transport charges stably, and to reflect a part of light passing through the charge transfer layer, and thereby enhancing out-coupling efficiency. In addition, the charge control layer regulates a charge flow from the electrode to the charge transfer layer, so that charges may be injected into an emitting material layer in a balanced manner.