OLED Hole Injection Layer Electron Transport Compound Balance

Solution Overview

Problem

In organic light-emitting devices, the use of materials with strong hole transport characteristics in the hole injection layer leads to an imbalance between hole and electron densities, resulting in decreased efficiency and lifespan due to the recombination zone formation at the interface of the electron transport layer.

Innovation Solution

Incorporating a first electron transport compound with weak hole transport capability in the hole injection layer, where the hole mobility is less than or equal to 0.95 times the electron mobility, to adjust the hole density and improve electron-hole balance, thereby enhancing efficiency and lifespan.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If materials with strong hole transport characteristics are used in the hole injection layer, then hole injection efficiency is improved, but electron-hole balance deteriorates due to excessive hole density

Engineering Contradiction:

Improvehole injection efficiencyVSAvoidelectron-hole balance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent changes the mobility parameter of the hole injection layer material from high hole mobility (conventional) to high electron mobility with low hole mobility. Specifically, the compound satisfies MH≤ME×0.95, fundamentally altering the transport characteristics to achieve better electron-hole balance while maintaining adequate hole injection.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies different material properties to different regions: the hole injection layer uses a compound with dominant electron transport capability (MH≤ME×0.95) to specifically address the interface region where recombination occurs, while other layers maintain their conventional material characteristics. This localized material optimization resolves the contradiction without compromising overall device structure.

Inventive Principle:

Principle #3Local quality

2Productivity

If materials with strong hole transport characteristics are used in the hole injection layer, then hole injection efficiency is improved, but device lifespan decreases due to recombination zone formation

Engineering Contradiction:

Improvehole injection efficiencyVSAvoiddevice lifespan

Core Design Contradiction:

ProductivityVSDuration of action of stationary object

Solution Approach 1:

The patent changes the mobility parameter of the hole injection layer material from high hole mobility (conventional) to high electron mobility with low hole mobility. Specifically, the compound satisfies MH≤ME×0.95, fundamentally altering the transport characteristics to achieve better electron-hole balance while maintaining adequate hole injection.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts the harmful effect of excessive hole accumulation (which causes recombination zone formation) into a beneficial effect by using a compound that inherently limits hole transport. The same property that prevents harmful recombination (low hole mobility) is achieved through the specific compound selection where electron mobility dominates, turning a potential disadvantage into a design advantage for extended device lifespan.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Productivity

If materials with strong hole transport characteristics are used in the hole injection layer, then hole injection efficiency is improved, but device efficiency decreases due to electron-hole imbalance

Engineering Contradiction:

Improvehole injection efficiencyVSAvoiddevice efficiency

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The patent changes the mobility parameter of the hole injection layer material from high hole mobility (conventional) to high electron mobility with low hole mobility. Specifically, the compound satisfies MH≤ME×0.95, fundamentally altering the transport characteristics to achieve better electron-hole balance while maintaining adequate hole injection.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS20220069248A1Light-emitting device and electronic apparatus including same

Publication Date: 2022.03.03 SAMSUNG DISPLAY CO LTD

AI summary

Provided is a light-emitting device including: a first electrode; a second electrode facing the first electrode; and an interlayer between the first electrode and the second electrode and including an emission layer, wherein the interlayer includes a hole injection layer and an electron transport layer, the hole injection layer includes a first electron transport compound, and a hole mobility (MH) and electron mobility (ME) of the first electron transport compound satisfy following Equation (1):Equation (1)MH≤ME×0.95 (1).