Organic Light Emitting Device Exciton Blocking Layer

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Solution Overview

Problem

Organic light emitting devices face reduced light emission efficiency due to exciton leakage from the green phosphorescent emission layer to the hole transport layer, resulting from endothermic energy transfer.

Innovation Solution

Incorporating an exciton blocking layer with a higher LUMO energy level than the green phosphorescent emission layer, positioned between the first electrode and the green emission layer, to prevent or reduce exciton leakage, utilizing compounds represented by Chemical Formula 1 or 2, with a LUMO energy level difference of 0.2 to 0.5 eV and a triplet energy level difference of 0.2 to 0.5 eV.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If an exciton blocking layer is inserted between the hole transport layer and the green phosphorescent emission layer, then light emission efficiency is improved by preventing exciton leakage, but device structure complexity increases

Engineering Contradiction:

Improvelight emission efficiencyVSAvoiddevice structure

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

An exciton blocking layer is introduced as an intermediary layer between the hole transport layer and the green phosphorescent emission layer. This layer has a higher LUMO energy level (by 0.2 to 0.5 eV) than the emission layer, creating an energy barrier that prevents exciton leakage while maintaining device functionality. The intermediary layer acts as a selective barrier that blocks excitons from migrating to the hole transport layer, thereby improving light emission efficiency without fundamentally altering the device's operational principles

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The exciton blocking layer is designed with specific energy level parameters - its LUMO energy level is set to be 0.2 to 0.5 eV higher than that of the green phosphorescent emission layer. This parameter optimization creates an appropriate energy barrier that effectively blocks exciton leakage while allowing other necessary charge transport processes to continue. By carefully controlling the energy level difference, the invention achieves improved efficiency without requiring drastic structural changes

Inventive Principle:

Principle #35Parameter changes

2Loss of energy

If the LUMO energy level difference between the exciton blocking layer and green emission layer is increased to prevent exciton leakage, then energy transfer efficiency is improved, but material selection complexity increases

Engineering Contradiction:

Improveenergy transfer efficiencyVSAvoidmaterial selection

Core Design Contradiction:

Loss of energyVSEase of manufacture

Solution Approach 1:

The invention specifies a precise LUMO energy level difference range of 0.2 to 0.5 eV between the exciton blocking layer and the green phosphorescent emission layer. This parameter optimization ensures sufficient energy barrier to prevent exciton leakage while avoiding excessive energy differences that would create other problems. The defined range provides clear material selection criteria, balancing energy transfer efficiency with practical material availability and ease of manufacture

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The exciton blocking layer is designed with specific local properties - it contains materials with particular LUMO energy levels and triplet energy levels that are tailored for this specific function. The layer uses compounds with specific molecular structures (as defined in Chemical Formulas 1 and 2 with specific substituent groups) to achieve the required energy level characteristics. This localized optimization of material properties at the interface between layers ensures effective exciton blocking while maintaining compatibility with adjacent layers

Inventive Principle:

Principle #3Local quality

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 increases the number of excitons in the green emission layer, enhancing light emission efficiency by blocking exciton leakage and ensuring efficient energy transfer.

Implementation Method 1

a LUMO energy level of the exciton blocking layer is higher than a LUMO energy level of the emission layer

Methodology Applied

Scientific EffectEnergy level difference (LUMO):

Implementation Method 2

preventing or reducing endothermic energy transfer in which the excitons are leaked to the hole transport layer from the green phosphorescent emission layer

Methodology Applied

Scientific EffectEndothermic energy transfer: Endothermic Reaction

Implementation Method 3

the triplet energy level of the material in the exciton blocking layer may be higher than a triplet energy level of the dopant material of the green emission layer

Methodology Applied

Scientific EffectTriplet energy level difference:

Data Source

PatentUS9048446B2Organic light emitting device

Publication Date: 2015.06.02 SAMSUNG DISPLAY CO LTD

AI summary

An organic light emitting device is described. The organic light emitting device includes: a substrate; a first electrode on the substrate; an emission layer on the first electrode; a second electrode on the emission layer; and an exciton blocking layer between the first electrode and the emission layer, in which a LUMO energy level of the exciton blocking layer is higher than a LUMO energy level of the emission layer.