Enhanced Drop-Cast Printing for Well-Oriented Organic Crystals

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Solution Overview

Problem

Conventional inkjet printing techniques fail to produce well-oriented organic crystals for the active channel region in organic field-effect transistors (OFETs), resulting in unsatisfactory carrier mobility and limiting their practical applications.

Innovation Solution

An enhanced drop-cast printing method using a two-liquid system, where a first liquid is placed on the drain electrode and a second liquid containing organic semiconductor species is added, allowing for isothermal crystallization and growth of well-oriented organic crystals due to hydrophilic-hydrophobic interaction, leading to improved electrical properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If conventional inkjet printing techniques are used to deposit organic semiconductor materials, then the manufacturing process is simple and cost-effective, but the organic crystals formed are not well-oriented and carrier mobility is unsatisfactory

Engineering Contradiction:

Improvemanufacturing simplicity and cost-effectivenessVSAvoidcrystal orientation quality

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent introduces a first liquid (water) as an intermediary substrate before depositing the organic semiconductor solution. This water layer acts as a mediator that enables the second liquid (organic semiconductor solution) to form well-oriented crystals through controlled evaporation and capillary action, resolving the contradiction between simple manufacturing and high crystal quality

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the physical parameters of the deposition process by using a two-liquid system with different evaporation rates. The first liquid (water) evaporates slower than the second liquid (organic solvent), creating controlled concentration gradients and capillary flows that导向 well-oriented crystal growth, thereby improving crystal orientation while maintaining process simplicity

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If solution-based processes are used for crystal growth, then the process is favorable for isotropic growth, but it is very difficult to grow well-oriented organic single crystals in the active channel region

Engineering Contradiction:

Improveprocess favorability for crystal growthVSAvoidcrystal orientation in active channel

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent applies local quality by creating different conditions in different regions of the deposited liquid. The water droplet creates a specific evaporation pattern and capillary flow structure that locally guides the organic semiconductor molecules to orient in a specific direction, transforming isotropic solution-based growth into anisotropic well-oriented crystal formation

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent performs preliminary action by first depositing the water droplet and allowing it to establish a stable evaporation pattern and capillary structure before adding the organic semiconductor solution. This preliminary preparation of the liquid interface creates favorable conditions for subsequent well-oriented crystal growth

Inventive Principle:

Principle #10Preliminary action

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 method achieves better electrical properties in OFETs with well-oriented organic crystals, enhancing carrier mobility and reducing trap densities, making them suitable for practical applications.

Implementation Method 1

hydrophilic-hydrophobic interaction between at least two different liquids

Methodology Applied

Scientific EffectHydrophilic-hydrophobic interaction: Hydrophile

Implementation Method 2

The evaporation rate of the first liquid is lower than that of the second liquid

Methodology Applied

Scientific EffectEvaporation: Evaporation

Implementation Method 3

direct growth of well-oriented organic crystals on an active channel region

Methodology Applied

Scientific EffectCrystallization: Crystallisation

Data Source

PatentUS8860008B2Forming active channel regions using enhanced drop-cast printing

Publication Date: 2014.10.14 SEOUL NATIONAL UNIVERSITY R&DB FOUNDATION

AI summary

An active region or channel for printed, organic or plastic electronics or polymer semiconductors, such as organic field-effect transistors (OFETs), is obtained by using an enhanced inkjet drop-cast printing technique. A two-liquid system is employed to achieve the direct growth of well-oriented organic crystals at the active region of channel. High-performance electrical properties exhibiting high carrier mobility and low threshold voltage are obtained due to the proper orientation of molecules in the grown crystal in a highest mobility direction, due to the absence of grain boundaries, and due to low trap densities. The hydrophobic-hydrophilic interactions between the liquids utilized, which results in the fabrication of low-cost and mass-producible printable electronic devices for applications in flexible displays, electronic signages, photovoltaic panels, membrane keyboards, radio frequency identification tags (RFIDs), electronic sensors, and integrated electronic circuits.