Cross-linked Polymer for OLED Hole Transport Layers
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Solution Overview
Problem
Current organic light emitting devices face challenges with materials that lack thermal stability, efficient charge transfer, and solvent resistance, leading to issues with high driving voltage, low efficiency, and short service life, particularly due to materials like NPB and PEDOT:PSS which have limitations in thermal stability and band gap alignment.
Innovation Solution
A polymer composition comprising specific units that form a cross-linked structure upon heat or light treatment, enhancing thermal and optical stability, and enabling efficient charge transfer, is used in the organic light emitting device, specifically in layers such as the hole transport and injection layers, to improve device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If NPB is used as hole transport layer material, then charge transport is achieved, but thermal stability is insufficient due to glass transition temperature of 100°C or less
Solution Approach 1:
The patent modifies the molecular structure of hole transport materials by introducing rigid aromatic groups (carbazole, triphenylamine) and extending conjugation systems, which fundamentally changes the glass transition temperature from 100°C or less to above 100°C, thereby achieving the required thermal stability for high current density operation
Solution Approach 2:
The patent employs composite material strategies by combining multiple functional moieties (carbazole, triphenylamine, fluorinated groups) within single molecular structures or creating blended systems that synergistically achieve both high glass transition temperature and effective charge transport properties
2Ease of manufacture
If PEDOT:PSS is used as hole transport material, then solution processability is achieved, but LUMO energy level is too low causing poor interface characteristics with light emitting layer
Solution Approach 1:
The patent applies local quality modification by introducing fluorinated groups at specific positions on the aromatic rings of hole transport materials, which locally alters the electron distribution and raises the LUMO energy level to achieve proper alignment with the light emitting layer while preserving overall solution processability
Solution Approach 2:
The patent systematically adjusts the LUMO energy level parameter by varying the degree and position of fluorination, molecular weight, and side chain structures, transforming the energy level from incompatible (too low) to compatible (properly aligned) with the light emitting layer
3Power
If conventional organic materials are used, then device operation is achieved, but driving voltage is high and efficiency is low due to poor charge transfer
Solution Approach 1:
The patent implements preliminary action by pre-optimizing the HOMO and LUMO energy levels of hole transport materials to ensure optimal energy level matching with adjacent layers before device assembly, which facilitates efficient charge transfer and reduces driving voltage requirements
Solution Approach 2:
The patent uses composite material design combining electron-donating groups (triphenylamine) and electron-deficient groups (fluorinated aromatic rings) to create materials with tailored energy levels that simultaneously achieve low driving voltage and high light efficiency through enhanced charge transfer
4Reliability
If materials with high charge mobility are used, then charge transport is improved, but thermal stability and solvent resistance deteriorate
Solution Approach 1:
The patent applies segmentation by separating the functional domains within the molecular structure - the core aromatic system provides charge transport pathways for high mobility, while peripheral rigid groups and fluorinated substituents provide thermal stability and solvent resistance, allowing both properties to coexist
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 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 composition comprising specific units that form a cross-linked structure upon heat or light treatment
Implementation Method 2
form a cross-linked structure upon heat or light treatment
Implementation Method 3
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
Implementation Method 4
The electrons and the holes which are injected into the organic material layer are recombined to form an exciton, and the exciton falls down again to the ground state to emit light
Data Source
Figure 1
AI summary
The present specification relates to a polymer including: a first unit represented by Formula 1; and a second unit represented by Formula 2, a coating composition including the same, and an organic light emitting device formed by using the same.