Coating Composition for OLED Hole Injection Layer 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 interface properties, leading to issues with high current handling, low voltage driving, and short device lifetime due to materials like NPB and PEDOT:PSS.
Innovation Solution
A coating composition comprising specific compounds represented by Chemical Formulas 1 and 2 is used to form organic material layers, which act as a dopant and host in the hole injection layer, enhancing thermal and chemical stability and charge mobility, and preventing solvent-induced migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If NPB is used as hole transfer layer material, then ease of manufacture is improved, but thermal stability deteriorates (glass transition temperature of 100°C or lower)
Solution Approach 1:
The patent modifies the chemical structure of hole transfer materials by introducing specific molecular configurations (as shown in the general formula) to elevate the glass transition temperature above 100°C while preserving charge transport properties, thereby resolving the contradiction between ease of manufacture and thermal stability
Solution Approach 2:
The patent develops composite hole transfer layer materials combining multiple organic compounds with complementary properties, where the composite structure achieves both high thermal stability (Tg > 100°C) and good charge transport, overcoming the limitations of single-component materials like NPB
2Ease of manufacture
If PEDOT:PSS is used as hole transfer material, then ease of manufacture is improved, but device efficiency and lifetime deteriorate (lower LUMO energy level compared to light emitting layer)
Solution Approach 1:
The patent adjusts the energy level parameters of hole transfer materials by modifying molecular structures to achieve appropriate HOMO and LUMO levels that are higher than those of light emitting layer materials, preventing electron injection from the hole transfer layer and thereby improving device efficiency and lifetime while maintaining solution processability
3Reliability
If materials with high charge mobility are used, then device efficiency is improved, but thermal stability may deteriorate
Solution Approach 1:
The patent creates composite materials combining charge transport components with thermally stable molecular backbones, achieving both high charge mobility and thermal stability (Tg > 100°C) simultaneously, thereby resolving the contradiction between device efficiency and thermal stability
Solution Approach 2:
The patent introduces specific functional groups and molecular motifs at strategic positions in the material structure to enhance charge mobility locally while maintaining overall thermal stability through the stable core structure, achieving both high efficiency and thermal resistance
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 coating composition enables long lifetime and efficient organic light emitting devices with improved thermal stability, charge transfer, and interface properties, allowing for high current handling and low voltage operation.
Implementation Method 1
An organic light emission phenomenon is one of examples converting a current to visible light by an internal process of specific organic molecules. When an organic material layer is placed between an anode and a cathode and a current is applied between the two electrodes, 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.
Implementation Method 2
materials used in an organic light emitting device need to have excellent chemical stability, charge mobility, and interface property with electrodes or adjacent layers. In other words, materials used in an organic light emitting device need to undergo less material deformation caused by moisture or oxygen.
Data Source
AI summary
The present specification relates to a coating composition comprising a compound, and an organic light emitting device comprising the same.