Aromatic Ester Solvents for Uniform OLED Inkjet Layer Deposition
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Solution Overview
Problem
The challenge in organic electronic devices is the poor performance of inkjet printing techniques for compositions containing semi-conductive organic host materials and luminescent metal complexes due to standard solvents, which result in poor drop directionality and layer quality.
Innovation Solution
A formulation comprising ester solvents with an aromatic group and specific organic functional materials, such as organometallic complexes, is developed to improve the deposition of organic semiconductor layers, ensuring uniformity and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If standard solvents are used for compositions containing semi-conductive organic host materials and luminescent metal complexes, then the composition can be prepared, but poor drop directionality and layer quality are obtained during inkjet printing
Solution Approach 1:
The patent changes the chemical parameters of the solvent by selecting esters with specific aromatic groups (benzoate, phenylacetate, phenoxyacetate structures) and controlling their physical properties (boiling point, surface tension, viscosity). This resolves the contradiction by optimizing solvent parameters to achieve both good printing performance and high layer quality simultaneously.
Solution Approach 2:
The aromatic ester solvent acts as an intermediary between the inkjet printing process and the organic functional materials. It mediates the deposition process by providing optimal solubility and evaporation characteristics, enabling both good drop directionality and uniform layer formation that standard solvents cannot achieve.
2Ease of operation
If standard solvents are used for depositing organic semiconductor layers, then the deposition process can be performed, but poor drop directionality is obtained
Solution Approach 1:
The patent optimizes solvent parameters including surface tension and viscosity by selecting specific aromatic esters. These parameter changes improve drop formation and directionality during inkjet printing while maintaining printing efficiency, resolving the contradiction between ease of operation and manufacturing precision.
3Ease of manufacture
If vacuum deposition processes are used for OLED fabrication, then device fabrication can be achieved, but cost savings and scale-up possibilities are limited compared to inkjet printing
Solution Approach 1:
The patent replaces the mechanical vacuum deposition system with a liquid-based inkjet printing system. By formulating organic functional materials in aromatic ester solvents, the patent enables precise material deposition through printing techniques, achieving both cost savings and scale-up possibilities while maintaining deposition homogeneity.
Solution Approach 2:
The patent changes the physical state of the functional materials from vapor phase (vacuum deposition) to liquid solution phase (inkjet printing). The aromatic ester solvents are specifically selected to provide optimal viscosity, surface tension, and evaporation rates, enabling homogeneous deposition through printing while reducing costs and improving scalability.
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 use of these ester solvents allows for effective ink deposition, forming uniform and well-defined organic layers with improved performance in OLEDs, enhancing layer properties and printing efficiency.
Implementation Method 1
liquid compositions (e.g. inkjet fluids) for forming an organic layer of an organic electronic device
Implementation Method 2
drying parameters are characteristics which can drastically influence the pixel pattern
Data Source
AI summary
The present invention relates to formulations for the preparation of organic electronic devices (OLEDs) which comprise (A) at least one specific ester solvent containing an aromatic group and (B) at least one organic functional material selected from organic conductors, organic semiconductors, organic fluorescent compounds, organic phosphorescent compounds, organic light-absorbent compounds, organic light-sensitive compounds, organic photosensitisation agents and other organic photoactive compounds, selected from organometallic complexes of transition metals, rare earth metals, lanthanides and actinides.