OLED P-type Dopant Diffusion Blocking Layer

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Solution Overview

Problem

Organic electroluminescence display devices face challenges in maintaining stable driving voltage over time and extending the driving lifetime of the light emitting layer due to p-type dopant diffusion, which affects the reliability and efficiency of the display.

Innovation Solution

Incorporating a P-type dopant diffusion blocking layer, typically a hexanitrile hexaazatriphenylene (HAT) layer, between the p-doped layer and the hole transport layer to prevent p-type dopant diffusion, thereby reducing driving voltage and enhancing the stability and longevity of the light emitting layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a p-doped layer is used to improve hole transport, then hole injection efficiency is improved, but p-type dopant diffusion into the light emitting layer causes voltage instability and reduced device lifetime

Engineering Contradiction:

Improvehole injection efficiencyVSAvoiddriving voltage stability

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

A diffusion blocking layer is introduced as an intermediary between the p-doped layer and the light emitting layer. This blocking layer prevents p-type dopant diffusion into the light emitting layer while maintaining effective hole transport, thus resolving the contradiction between hole injection efficiency and driving voltage stability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The hole transport function is segmented into two distinct layers: a p-doped layer for efficient hole injection and a diffusion blocking layer for preventing dopant migration. This segmentation allows each layer to specialize in its function without interfering with the other, solving the contradiction between hole transport efficiency and voltage stability.

Inventive Principle:

Principle #1Segmentation

2Illumination intensity

If a p-doped layer is used to enhance device performance, then initial brightness is improved, but device lifetime is reduced due to dopant diffusion

Engineering Contradiction:

ImprovebrightnessVSAvoiddriving lifetime

Core Design Contradiction:

Illumination intensityVSDuration of action of moving object

Solution Approach 1:

The diffusion blocking layer acts as a protective intermediary that preserves the light emitting layer from dopant contamination. This allows the p-doped layer to maintain high brightness performance while the blocking layer ensures long-term device lifetime by preventing degradation mechanisms.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The diffusion blocking layer is positioned in advance to cushion against the harmful effect of dopant diffusion before it can reach the light emitting layer. This preventive measure ensures both high initial brightness and extended device lifetime by eliminating the degradation pathway.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Stability of the object's composition

If the organic layer thickness is increased to improve color stability, then color stability is improved, but driving voltage increases

Engineering Contradiction:

Improvecolor stabilityVSAvoiddriving voltage

Core Design Contradiction:

Stability of the object's compositionVSPower

Solution Approach 1:

The introduction of the diffusion blocking layer changes the electrical parameters of the device structure. By adding this thin functional layer, the device achieves improved color stability through optimized layer composition while the blocking layer's properties help manage the driving voltage characteristic.

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 effectively reduces the driving voltage and extends the lifetime of the organic electroluminescence display device by preventing p-type dopant diffusion, ensuring stable performance over time while maintaining excellent color stability and contrast.

Implementation Method 1

a P-type dopant diffusion blocking layer on the p-doped layer

Methodology Applied

Scientific EffectDiffusion: Diffusion

Implementation Method 2

The excitons transition from an excited state to a ground state, so that fluorescent molecules of the light emitting layer EML emit light

Methodology Applied

Scientific EffectFluorescence: Fluorescence

Implementation Method 3

light generated in the light emitting layer EML is iteratively reflected between the anode electrode and the cathode electrode, so that light of a corresponding peak wavelength resonates and is emphasized

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS8927980B2Organic electroluminescence display device

Publication Date: 2015.01.06 SAMSUNG DISPLAY CO LTD

AI summary

An organic electroluminescence display device includes a p-doped layer doped with a P-type dopant on an anode electrode, a P-type dopant diffusion blocking layer on the p-doped layer, a first hole transport layer on the P-type dopant diffusion blocking layer, a light emitting layer on the first hole transport layer, an electron transport layer on light emitting layer, and a cathode electrode on the electron transport layer, the p-doped layer, the P-type dopant diffusion blocking layer, the hole transport layer, and the light emitting layer being stacked in the stated order on the anode.