Organic Field Effect Transistor Gate Electrode Separation

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Solution Overview

Problem

The widespread application of organic field effect transistors (OFETs) is limited due to their low performance and stability, despite advancements in thin and flexible circuit capabilities, as they struggle to achieve optimal working parameters and inversion channel formation.

Innovation Solution

An organic field effect transistor design featuring a gate electrode separation with an electrically doped organic semiconducting layer directly on the gate electrode, comprising an organic matrix material and dopant, along with additional doped layers for improved electrical contact and a pin-layer structure, allowing for efficient charge carrier injection and reduced parasitic leakage currents.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional organic FET structures are used, then the device can be manufactured with simple processes, but the performance and stability remain low

Engineering Contradiction:
Improveperformance and stabilityVSAvoidstructure complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The gate electrode separation is segmented into multiple functional layers: an inorganic gate insulator layer and an organic interface layer with doped regions. This segmentation allows each layer to perform its specific function optimally, improving overall device reliability while maintaining manufacturability through established layer-by-layer fabrication processes.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The organic interface layer incorporates localized doped regions with different doping types (n-type and p-type) at specific positions adjacent to the source and drain electrodes. This local quality variation enables precise control of charge carrier injection and reduces parasitic leakage currents, thereby enhancing performance without requiring complete structural redesign.

Inventive Principle:
Principle #3Local quality

2Reliability

If doping is applied to reduce contact resistance, then charge carrier injection is enhanced, but threshold voltage control becomes difficult due to contact doping effects

Engineering Contradiction:
Improvecharge carrier injectionVSAvoidthreshold voltage control
Core Design Contradiction:
ReliabilityVSManufacturing precision

Solution Approach 1:

The invention extracts the doping function from the contact regions and relocates it to the organic interface layer adjacent to the contacts. By placing doped regions in the interface layer rather than directly at the metal-semiconductor contact, the design separates contact resistance reduction from threshold voltage control, allowing independent optimization of both parameters.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The organic interface layer acts as an intermediary between the metal electrodes and the intrinsic organic semiconductor channel. The doped regions within this interface layer mediate the charge transfer process, providing efficient charge carrier injection while the intrinsic channel region maintains clean threshold voltage characteristics不受contact doping interference.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Reliability

If inversion channel formation is attempted in organic MIS capacitors, then the transistor can operate in inversion regime, but the inversion regime cannot be reached due to material limitations

Engineering Contradiction:
Improveinversion channel formationVSAvoidoperating regime flexibility
Core Design Contradiction:
ReliabilityVSAdaptability or versatility

Solution Approach 1:

The invention changes the electrical parameters of the organic interface layer through controlled doping, transforming it from an intrinsic to a doped semiconductor layer. This parameter change enables the formation of inversion channels by creating appropriate potential gradients at the semiconductor-insulator interface, allowing organic FETs to operate in the inversion regime similar to silicon devices.

Inventive Principle:
Principle #35Parameter changes

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 solution enhances the performance and stability of OFETs by optimizing working parameters, enabling efficient charge carrier injection and reducing leakage currents, thus improving the overall functionality and potential applications of OFETs.

Implementation Method 1

The doped organic semiconducting layer comprises an organic matrix material and an organic electrical dopant

Methodology Applied
Scientific EffectElectrical doping: Dopants

Implementation Method 2

enabling efficient charge carrier injection

Methodology Applied
Scientific EffectCharge carrier injection: Conduction (electrical)

Implementation Method 3

reducing leakage currents

Methodology Applied
Scientific EffectPotential barrier formation: Diode

Data Source

PatentEP2790238B1Organic field effect transistor and method for production
Publication Date: 2018.08.22 NOVALED GMBH
  • EP2790238B1 patent drawingFigure 1a~1b
  • EP2790238B1 patent drawingFigure 1c~1d
  • EP2790238B1 patent drawingFigure 2~3

AI summary

The present disclosure relates to an organic field effect transistor, comprising a first electrode (1) and a second electrode (2), the electrodes providing a source electrode and a drain electrode, a gate electrode (6), an electronically active region at least in part made of an organic material and providing a charge a carrier channel, and a gate electrode separation, comprising a doped organic semiconducting layer directly provided on the gate electrode (6), wherein the doped organic semiconducting layer comprises an organic matrix material and an organic dopant. Furthermore, a method for producing an organic field effect transistor is provided.