Lateral Channel OLET Pixel Architecture for Enhanced Mobility

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Solution Overview

Problem

Conventional OLET-based display pixels with vertical light emitting transistors suffer from limitations in charge carrier mobility due to vertical charge transport, which is several orders of magnitude lower than lateral field effect, leading to suboptimal electrical device characteristics.

Innovation Solution

The proposed pixel architecture incorporates a lateral channel field-effect transistor as a driving transistor for the OLET, featuring horizontally separated source and drain electrodes with vertical overlap with the gate electrode, enabling lateral charge transport and improved electrical characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a vertical light emitting transistor is used in OLET-based display pixels, then the device structure is simplified and manufacturing is easier, but the charge carrier mobility is several orders of magnitude lower due to vertical charge transport

Engineering Contradiction:
Improveease of manufactureVSAvoidelectrical device characteristics
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The patent inverts the conventional vertical charge transport architecture by implementing a lateral channel field-effect transistor where charge carriers move horizontally between source and drain electrodes. This inversion resolves the contradiction by achieving both ease of manufacture through simplified device structure and improved electrical characteristics through enhanced charge carrier mobility in the lateral direction.

Inventive Principle:
Principle #13The other way round (Inversion)

Solution Approach 2:

The patent transitions from vertical charge transport (one-dimensional) to lateral charge transport (two-dimensional planar movement). By changing the dimensionality of charge carrier movement from vertical to lateral, the patent simultaneously maintains manufacturing simplicity while dramatically improving charge carrier mobility and electrical device characteristics.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Power

If the channel length is shortened to achieve high output current using organic semiconductors, then the output current increases, but high resolution patterning is required which increases manufacturing cost

Engineering Contradiction:
Improveoutput currentVSAvoidease of manufacture
Core Design Contradiction:
PowerVSEase of manufacture

Solution Approach 1:

The patent inverts the conventional lateral channel approach by using a vertical field effect transistor geometry where the channel length is defined by the thickness of the semiconductor thin film rather than the lateral distance between source and drain electrodes. This allows submicron channel lengths to be achieved without requiring high resolution patterning, thus maintaining ease of manufacture while achieving high output current.

Inventive Principle:
Principle #13The other way round (Inversion)

Solution Approach 2:

The patent moves the channel length definition from the lateral dimension to the vertical dimension (film thickness). This dimensional transition allows precise control of channel length at submicron scales through thin film deposition techniques rather than requiring high resolution lithographic patterning, thereby maintaining manufacturing simplicity while achieving high output current.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

3Reliability

If a lateral channel field-effect transistor is used as driving transistor, then charge carrier mobility is improved and electrical characteristics are enhanced, but the device complexity increases compared to vertical configurations

Engineering Contradiction:
Improveelectrical device characteristicsVSAvoiddevice complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the driving transistor and light emitting transistor functions into a single integrated lateral channel field-effect transistor structure. By combining these functions, the patent reduces overall device complexity while maintaining the improved charge carrier mobility and electrical characteristics associated with lateral charge transport.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The patent implements a multi-functional lateral channel field-effect transistor that simultaneously serves as both the driving transistor and the light emitting transistor. This universal structure performs multiple functions (charge transport, light emission, and driving control) within a single device architecture, reducing complexity while achieving superior electrical characteristics.

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

This configuration enhances the driving of the OLET, improves electrical device characteristics, and increases the aperture ratio and brightness of the display pixels by allowing better lateral charge transport and simpler driving mechanisms.

Implementation Method 1

an organic semiconductor light-emitting layer capable of emitting light by recombination of holes and electrons

Methodology Applied
Scientific EffectRecombination of holes and electrons: Electroluminescence

Data Source

PatentEP3218945B1Display containing improved pixel architectures
Publication Date: 2021.05.26 FLEXTERRA INC
  • EP3218945B1 patent drawingFigure 1
  • EP3218945B1 patent drawingFigure 2A~2B
  • EP3218945B1 patent drawingFigure 3~4

AI summary

The invention relates to improved Organic Light Emitting Transistor (OLET) pixel architecture for OLET based displays.