Hole Transport Polymer for OLED Thermal Stability
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Solution Overview
Problem
Current organic light emitting devices face challenges with materials that lack thermal stability, efficient charge transfer, chemical stability, and solvent tolerance, leading to issues with high current handling, low voltage driving, and long-term reliability due to limitations in hole and electron mobility, as well as interface properties with electrodes.
Innovation Solution
A polymer incorporating specific units represented by Chemical Formula 1 and 2, which include a curing group for solvent tolerance and heat or light-induced crosslinking, is used in a coating composition for forming organic light emitting devices, enhancing film stability and performance by controlling glass transition temperature and solubility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If NPB is used as a hole transfer layer material, then the device can be manufactured with current materials, but the glass transition temperature is 100°C or lower making it difficult to use in high current devices
Solution Approach 1:
The patent modifies the molecular structure of hole transfer materials by introducing rigid aromatic groups (naphthyl, phenyl, biphenyl) and adjusting substituent positions to elevate the glass transition temperature from 100°C to above 150°C, thereby improving thermal stability for high current applications
Solution Approach 2:
The invention creates composite hole transfer materials combining electron-donating arylamine groups with electron-withdrawing groups, achieving both high thermal stability and optimal charge transport properties that single-component materials cannot provide
2Ease of manufacture
If PEDOT:PSS is used as a hole transfer material, then solution coating can be applied, but the LUMO energy level is lower than light emitting layer materials causing efficiency and lifetime problems
Solution Approach 1:
The patent precisely adjusts the HOMO and LUMO energy levels of hole transfer materials through molecular design, ensuring the LUMO level is higher than light emitting layer materials to prevent electron injection issues while maintaining solution processability
Solution Approach 2:
The invention introduces intermediate hole transfer layers with specifically engineered energy levels that act as mediators between the electrode and light emitting layer, facilitating smooth charge transfer while preventing direct contact between PEDOT:PSS and the light emitting layer
3Productivity
If materials with high charge mobility are used, then exciton formation efficiency improves, but thermal stability and chemical stability may be compromised
Solution Approach 1:
The patent designs composite molecular structures combining highly mobile charge transport segments with thermally stable aromatic backbones, achieving both high charge mobility for efficient exciton formation and thermal/chemical stability for device reliability
Solution Approach 2:
The invention creates materials with localized functional regions where specific molecular segments provide charge mobility while other segments provide thermal and chemical stability, allowing optimization of different properties in different parts of the molecular structure
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 composition enables the formation of organic light emitting devices with improved thermal stability, low driving voltage, high light emission efficiency, and extended lifetime by providing solvent tolerance and uniform film formation, thus overcoming previous material limitations.
Implementation Method 1
a curing group for solvent tolerance and heat or light-induced crosslinking
Implementation Method 2
heat or light-induced crosslinking
Implementation Method 3
a storable homogeneous solution needs to be formed
Implementation Method 4
electrons and holes are injected to the organic material layer from the cathode and the anode, respectively. The holes and the electrons injected to the organic material layer recombine to form excitons, and light emits when these excitons fall back to the ground state
Data Source
Figure 1~2
Figure 3~4
AI summary
The present disclosure relates to a polymer including a unit represented by Chemical Formula 1 and a unit represented by Chemical Formula 2, a coating composition including the polymer, and an organic light emitting device formed using the same.