Organic Semiconductor Formulation Viscosity Control
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Solution Overview
Problem
Current methods for preparing organic semiconductor (OSC) formulations for organic electronic devices face challenges in achieving suitable viscosity and solvent selection, which affects the performance and lifetime of devices like OFETs and OPV cells, as existing solutions lack clear guidance on selecting suitable solvents and often require non-volatile additives that can harm device performance.
Innovation Solution
A method of preparing OSC formulations by selecting solvents based on their partition ratio (log P) and viscosity, with a weighted average log P >1.5 and viscosity >10 cP at 25°C, without additives, allowing for precise solvent selection and avoiding the need for thickening agents, while ensuring the solvents dissolve OSC compounds effectively and have suitable viscosities for printing techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If low viscosity solvents (10 cP) are used for good print quality, then printing performance is improved, but device performance deteriorates due to inability to dissolve OSC materials effectively
Solution Approach 1:
The patent changes the viscosity parameter from the conventional low range (10 cP) to a higher range (25-5000 cP, preferably 50-1000 cP) by selecting specific high boiling point solvents. This parameter change enables effective dissolution of OSC materials while maintaining suitability for printing processes, resolving the contradiction between print quality and device performance.
Solution Approach 2:
The patent employs composite solvent systems combining high boiling point solvents (providing high viscosity and dissolution power) with low boiling point solvents (providing volatility for drying). This composite approach allows the formulation to exhibit both high viscosity for material dissolution and appropriate evaporation characteristics for printing, simultaneously achieving device performance and print quality.
2Ease of operation
If viscosity modifiers (silica, clays, polymers) are added to increase viscosity above 10 cP, then viscosity is improved, but device performance is destroyed
Solution Approach 1:
The patent extracts and eliminates harmful viscosity modifiers (silica, clays, high molecular weight polymers) from the formulation. Instead, it achieves the required viscosity (25-5000 cP) through the intrinsic properties of high boiling point solvents (water, glycols, esters, ketones), thereby maintaining both high viscosity and device performance without the detrimental effects of conventional additives.
Solution Approach 2:
The patent replaces permanent viscosity modifiers with volatile high boiling point solvents that serve their viscosity function temporarily during printing and then evaporate completely. These solvents (water, glycols, esters, ketones) provide the necessary viscosity during processing but leave no residual effect on the final device, unlike persistent additives such as silica or polymers.
3Ease of operation
If hydrophilic solvents are used to achieve high viscosity ranges, then viscosity is improved, but solubility of OSC materials deteriorates
Solution Approach 1:
The patent uses composite solvent systems combining hydrophilic high boiling point solvents (water, glycols) with hydrophobic components (esters, ketones, aromatic hydrocarbons). This composite approach enables the formulation to achieve high viscosity through the hydrophilic solvents while the hydrophobic components ensure effective dissolution of the typically hydrophobic OSC materials, resolving the solubility-viscosity contradiction.
4Productivity
If traditional printing technologies (flexographic, gravure) are used, then manufacturing scalability is improved, but formulation requirements become more complex
Solution Approach 1:
The patent changes the formulation parameters to match the requirements of traditional printing technologies. By formulating inks with viscosities of 25-5000 cP using high boiling point solvents, the patent enables compatibility with flexographic and gravure printing processes, thereby achieving manufacturing scalability without requiring complex formulation adjustments for each printing method.
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
This approach enables the development of OSC formulations that maintain device performance by ensuring solvents dissolve OSC compounds effectively and have suitable viscosities for printing, reducing the need for non-volatile additives and enhancing the precision of solvent selection, leading to improved OSC formulations and devices.
Implementation Method 1
dissolving an organic semiconducting (OSC) compound in a solvent or in a solvent blend comprising two or more solvents
Implementation Method 2
removing the solvent(s), for example by evaporation
Data Source
AI summary
The invention relates to a process for preparing a formulation comprising an organic semiconductor (OSC) and one or more organic solvents, to novel formulations obtained by this process, to their use as coating or printing inks for the preparation of organic electronic (OE) devices, especially organic field effect transistors (OFET) and organic photovoltaic (OPV) cells, to a process for preparing OE devices using the novel formulations, and to OE devices prepared from such a process or from the novel formulations.