OLED Hole Acceleration Layer Reduces Driving Voltage

Solution Overview

Problem

Conventional OLEDs face high power consumption due to the relatively low hole mobility of the hole injection layer (HIL), which increases the driving voltage and power consumption, even when formed to appropriate thicknesses for optimal chromaticity coordinates.

Innovation Solution

Incorporating a hole acceleration layer (HAL) with higher hole mobility than the HIL between the HIL and the hole transport layer (HTL) to enhance luminance and reduce power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If the HIL and HTL are formed to appropriate thicknesses to realize NTSC chromaticity coordinates, then chromaticity quality is improved, but driving voltage increases due to the HIL's relatively low hole mobility, resulting in high power consumption

Engineering Contradiction:

Improvechromaticity coordinatesVSAvoidpower consumption

Core Design Contradiction:

Illumination intensityVSUse of energy by moving object

Solution Approach 1:

The hole transport function is segmented into three distinct layers: HIL for hole injection, HAL for hole acceleration, and HTL for hole transport to emission region. This segmentation allows each layer to be optimized for its specific function, with the HAL providing high hole mobility to reduce driving voltage while maintaining appropriate thicknesses of HIL and HTL for chromaticity quality.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The HAL acts as an intermediary layer between the HIL and HTL, providing a high-hole-mobility pathway that accelerates hole transport. This intermediary layer with superior hole mobility (5×10^-4 to 10^-3 cm²/Vs) reduces the overall driving voltage required while maintaining the chromaticity coordinates achieved by the optimized HIL and HTL thicknesses.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the HIL is formed with sufficient thickness to facilitate hole injection, then hole injection efficiency is improved, but the overall organic layer thickness increases, leading to higher driving voltage

Engineering Contradiction:

Improvehole injection efficiencyVSAvoiddriving voltage

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The hole transport function is segmented into three distinct layers: HIL for hole injection, HAL for hole acceleration, and HTL for hole transport to emission region. This segmentation allows each layer to be optimized for its specific function, with the HAL providing high hole mobility to reduce driving voltage while maintaining appropriate thicknesses of HIL and HTL for chromaticity quality.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The hole mobility parameter is significantly changed in the HAL layer (5×10^-4 to 10^-3 cm²/Vs) compared to conventional structures. This parameter change allows the HAL to accelerate hole transport efficiently, reducing the required thickness of the overall hole transport stack while maintaining injection efficiency and reducing driving voltage.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS7659543B2Organic light emitting display and method of fabricating the same

Publication Date: 2010.02.09 SAMSUNG DISPLAY CO LTD

AI summary

An organic light emitting display including a pixel electrode arranged on a substrate, an organic layer arranged on the pixel electrode and including at least a hole injection layer, a hole acceleration layer, a hole transport layer, and an emission layer, and an opposite electrode arranged on the organic layer. The hole acceleration layer is formed of a material having a hole mobility that is higher than that of the hole injection layer.