Organic EL Gate Electrode Parasitic Transistor Isolation

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Solution Overview

Problem

Existing organic EL displays suffer from electrical color mixing (crosstalk) due to parasitic transistors and pitch narrowing, leading to reduced image quality and NTSC ratio.

Innovation Solution

Incorporating a gate electrode between adjacent bottom electrodes to limit the channel expansion of parasitic transistors, thereby reducing leakage current and preventing electrical color mixing, with the gate electrode preferably surrounding the bottom electrodes and embedded within the interlayer film to minimize light deflection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If bottom electrodes are arranged at an interval to form pixels, then pixel structure is established, but parasitic transistors are formed between adjacent pixels causing leakage current and electrical color mixing

Engineering Contradiction:

Improvepixel structure formationVSAvoidelectrical color mixing

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The invention divides the continuous space between bottom electrodes by introducing gate electrodes that extend from side walls, effectively segmenting the parasitic transistor channels and isolating adjacent pixels electrically

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Gate electrodes are introduced as intermediary structures between adjacent bottom electrodes to control and block the formation of parasitic transistor channels, preventing leakage current without affecting the normal pixel operation

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If pitch of bottom electrodes is narrowed to increase pixel density, then more pixels per area are achieved, but electrical color mixing increases due to closer proximity

Engineering Contradiction:

Improvepixel densityVSAvoidelectrical color mixing

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The invention transitions from two-dimensional planar spacing to three-dimensional side wall extension, allowing pitch narrowing in the planar direction while maintaining electrical isolation through vertical gate electrode extensions

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

Gate electrodes are selectively positioned at critical regions where parasitic transistors form between adjacent bottom electrodes, providing localized electrical isolation only where needed while maintaining high pixel density elsewhere

Inventive Principle:

Principle #3Local quality

3Reliability

If gate electrode is added to prevent parasitic transistor, then electrical color mixing is reduced, but device structure becomes more complex

Engineering Contradiction:

Improveelectrical color mixingVSAvoiddevice structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The gate electrode structure is merged with the existing pixel architecture, utilizing the same fabrication processes and integrating seamlessly with bottom electrodes and organic light emitting layers

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The gate electrode structure serves multiple functions: blocking parasitic transistor channels, maintaining pixel isolation, and potentially serving as additional electrode connections, reducing the need for separate isolation structures

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

Effectively reduces electrical color mixing and light deflection, enhancing image quality and NTSC ratio by limiting leakage current and channel expansion, while simplifying manufacturing processes through shared formation with wiring layers.

Implementation Method 1

a gate electrode, which is placed at a region between mutually adjacent bottom electrodes in a planar view seen from a normal direction of a surface of the base layer, for turning off a parasitic transistor formed by cooperation of the top electrode and mutually adjacent bottom electrodes

Methodology Applied

Scientific EffectElectric Field: Electric Field

Data Source

PatentUS9161397B2Organic EL device

Publication Date: 2015.10.13 ROHM CO LTD

AI summary

An organic EL device of the present invention includes: a base layer; a plurality of bottom electrodes arranged in a surface portion of the base layer at an interval in a lateral direction along a surface of the base layer; an organic layer which contains an organic light emitting material and is placed on the base layer so as to cover the plurality of bottom electrodes collectively and divided into a plurality of pixels respectively corresponding to the plurality of bottom electrodes; a top electrode opposed to the plurality of bottom electrodes with the organic layer interposed therebetween; and a gate electrode, which is placed at a region between mutually adjacent bottom electrodes in a planar view seen from the normal direction of the surface of the base layer, for turning off a parasitic transistor formed by cooperation of the top electrode and mutually adjacent bottom electrodes.