OLED Hole Transport Polymer Cross-Linking
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Solution Overview
Problem
Current organic light emitting devices face challenges with materials that lack thermal stability, efficient charge mobility, and solvent resistance, leading to issues with high driving voltage, low light efficiency, and short service life, particularly due to the limitations of materials like NPB and PEDOT:PSS.
Innovation Solution
A polymer comprising specific units with curing groups, allowing for cross-linking through heat or UV treatment, is used to form a stable and efficient organic material layer for OLEDs, enhancing thermal and optical stability, solvent resistance, and improving layer uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If NPB is used as hole transport layer material, then the device can be manufactured with conventional materials, but the thermal stability is insufficient due to glass transition temperature of 100°C or less
Solution Approach 1:
The patent uses a copolymer comprising a first unit (Formula 1) with hole transport capability and a second unit (Formula 2) with curing group, combining the functions of hole transport and thermal stabilization in a single material system, achieving both adequate hole transport and high thermal stability (Tg ≥ 100°C)
Solution Approach 2:
The patent changes the molecular structure parameters by introducing rigid aromatic groups (naphthyl, phenyl, biphenyl) and curing groups into the polymer backbone, which increases the glass transition temperature and thermal stability while maintaining hole transport properties through the aromatic amine structure
2Ease of manufacture
If PEDOT:PSS is used as hole transport material, then the device can be manufactured by solution application method, but the LUMO energy level is lower than the light emitting layer material causing poor interface characteristics
Solution Approach 1:
The patent designs the copolymer with specific local structural features: the first unit (Formula 1) provides hole transport capability with appropriate HOMO level, while the second unit (Formula 2) provides curing functionality and adjusts the energy level profile, creating local functional zones within the polymer chain that address both manufacturing ease and interface compatibility
Solution Approach 2:
The patent adjusts the energy level parameters by modifying the aromatic amine structure and substituent groups in Formula 1, raising the HOMO and LUMO levels to be higher than the light emitting layer material, while maintaining solution processability through the polymer structure
3Device complexity
If conventional organic materials are used, then the device structure is simple, but the charge mobility is insufficient leading to high driving voltage
Solution Approach 1:
The patent creates a continuous conjugated pathway through the copolymer structure with aromatic amine units (Formula 1) that facilitate continuous hole transport from the electrode through the organic layer, reducing charge accumulation and lowering the driving voltage required for operation
4Ease of manufacture
If materials without curing groups are used, then the manufacturing process is simpler, but the solvent resistance and chemical stability are poor
Solution Approach 1:
The patent incorporates curing groups (Formula 2) into the copolymer structure in advance, allowing the material to form cross-linked networks during or after device fabrication, providing preemptive protection against solvent attack and chemical degradation before they can damage the device
Solution Approach 2:
The patent combines linear polymer chains with cross-linking functionality, creating a composite structure that maintains the processability of linear polymers during manufacturing while developing the solvent resistance of cross-linked networks upon curing
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 polymer solution reduces driving voltage, enhances light efficiency, and extends the service life of organic light emitting devices by providing improved thermal and optical stability and solvent resistance.
Implementation Method 1
A polymer comprising specific units with curing groups, allowing for cross-linking through heat or UV treatment
Implementation Method 2
allowing for cross-linking through heat or UV treatment, is used to form a stable and efficient organic material layer
Implementation Method 3
The polymer solution reduces driving voltage, enhances light efficiency, and extends the service life of organic light emitting devices by providing improved thermal and optical stability and solvent resistance
Implementation Method 4
An organic light emission phenomenon is one of the examples of converting an electric current into visible rays through an internal process of a specific organic molecule
Data Source
Figure 1
AI summary
The present specification relates to a polymer comprising: a first unit represented by Formula 1; and a second unit represented by Formula 2, a coating composition comprising the same, and an organic light emitting device formed by using the same.