Interlayer Composition for Adhesion and Conductivity in OTFTs

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Solution Overview

Problem

Current silver nanoparticle inks face challenges with adhesion to substrates like glass and polyimide, leading to inadequate mechanical robustness and potential loss of electrical conductivity, while also requiring improved film forming and ink wettability for high-performance printed organic thin-film transistors (OTFTs) with controlled line width and low off-state leakage current.

Innovation Solution

An interlayer composition comprising an epoxy compound, polyvinyl phenol, melamine resin, solvent, optional surfactant, and catalyst is used to form a cured film that enhances adhesion, wettability, and conductivity, serving as a back channel dielectric layer for OTFTs, allowing for precise line width control and reduced off-state leakage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If silver nanoparticle inks are used for printed conductors, then high conductivity is achieved, but adhesion to substrates is poor

Engineering Contradiction:
Improveelectrical conductivityVSAvoidadhesion to substrate
Core Design Contradiction:
ReliabilityVSStrength

Solution Approach 1:

An interlayer composition comprising epoxy compound, polyvinyl phenol, and melamine resin is introduced between the substrate and silver nanoparticle ink. This interlayer serves as a mediator that enhances adhesion of the conductive ink to the substrate while maintaining electrical conductivity, resolving the contradiction between poor adhesion and high conductivity requirements

Inventive Principle:
Principle #24Intermediary (Mediator)

2Ease of manufacture

If conventional substrates like glass and polyimide are used, then device fabrication is enabled, but ink wetting and adhesion are inadequate

Engineering Contradiction:
Improvedevice fabrication capabilityVSAvoidink wetting and adhesion
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The interlayer composition acts as an intermediary between conventional substrates (glass, polyimide) and the conductive ink. It modifies the substrate surface properties to enable better ink wetting and adhesion while maintaining compatibility with existing device fabrication processes

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The interlayer is formed as a composite material combining epoxy compound, polyvinyl phenol, and melamine resin. This composite structure provides synergistic effects that enhance both adhesion and wettability properties, overcoming the limitations of conventional single-material substrates

Inventive Principle:
Principle #40Composite materials

3Strength

If interlayer composition is applied to enhance adhesion, then mechanical robustness is improved, but manufacturing complexity increases

Engineering Contradiction:
Improvemechanical robustnessVSAvoidmanufacturing process complexity
Core Design Contradiction:
StrengthVSDevice complexity

Solution Approach 1:

Multiple functions (adhesion enhancement, wettability improvement, mechanical robustness) are merged into a single interlayer composition. This eliminates the need for separate treatment steps, reducing manufacturing complexity while achieving enhanced mechanical and electrical properties

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The interlayer composition is designed to perform multiple functions simultaneously: enhancing adhesion, improving ink wettability, providing mechanical robustness, and maintaining electrical conductivity. This multi-functionality reduces the number of required layers and simplifies the overall manufacturing process

Inventive Principle:
Principle #6Universality (Multi-functionality)

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 interlayer composition achieves superior adhesion and conductivity, enabling well-defined conductive line widths and low off-state leakage currents, thereby improving the performance of OTFTs and ensuring robust mechanical properties without compromising electrical conductivity.

Implementation Method 1

wherein the interlayer comprises a cured film obtainable from a polymerisation reaction of an interlayer composition

Methodology Applied
Scientific EffectPolymerization reaction:

Implementation Method 2

The interlayer composition achieves superior adhesion and conductivity

Methodology Applied
Scientific EffectAdhesion: Adhesive

Implementation Method 3

wherein the interlayer serves as a back channel dielectric layer for the device

Methodology Applied
Scientific EffectDielectric property: Dielectric

Data Source

PatentEP3276691B1Device comprising dielectric interlayer
Publication Date: 2022.11.02 PALO ALTO RESEARCH CENTER INC
  • EP3276691B1 patent drawingFigure 1~2
  • EP3276691B1 patent drawingFigure 3A~3C
  • EP3276691B1 patent drawingFigure 3D~3E

AI summary

A process for preparing a device and a device including a substrate; an interlayer disposed on the substrate, wherein the interlayer comprises a cured film formed from an interlayer composition, wherein the interlayer composition comprises: an epoxy compound; a polyvinyl phenol; a melamine resin; a solvent; an optional surfactant; and an optional catalyst; a source electrode and a drain electrode disposed on a surface of the interlayer; a semiconductor layer disposed on the interlayer, wherein the semiconductor layer is disposed into a gap between the source and drain electrode; a back channel interface comprising an interface between the semiconductor layer and the interlayer, wherein the interlayer serves as a back channel dielectric layer for the device; a dielectric layer disposed on the semiconductor layer; a gate electrode disposed on the dielectric layer. Also an interlayer composition and an organic thin film transistor comprising the interlayer composition.