N-doped Semiconducting Material for OLED Cathodes

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Solution Overview

Problem

Current methods for n-doping in organic electronic devices, particularly for OLEDs, face challenges with caesium's high reactivity, volatility, and air/moisture sensitivity, leading to handling difficulties and quality assurance issues, while alternative dopants like lithium and metal complexes have limitations in conductivity and operational voltage optimization.

Innovation Solution

Employing substantially air-stable metals such as alkali, alkaline earth, and rare earth metals, along with specific polar compounds like phosphine oxides and diazoles, to create semiconducting materials with improved electrical properties, allowing for efficient electron transport and injection in OLEDs, using a process that involves co-evaporation and codeposition under reduced pressure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If caesium is used as n-dopant in organic electronic devices, then electrical conductivity is improved, but handling difficulty and safety hazard increase due to high reactivity and air/moisture sensitivity

Engineering Contradiction:

Improveelectrical conductivityVSAvoidhandling difficulty

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent uses an organic compound as an intermediary carrier to deliver caesium atoms to the electron transporting layer. The caesium is first deposited as caesium atoms on an organic compound layer, which then transfers these atoms to the ETL during subsequent processing. This intermediary approach allows caesium to be handled in a stable organic compound form rather than as reactive metallic caesium, solving the handling difficulty while maintaining the electrical conductivity benefits.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If caesium is used as n-dopant, then electrical conductivity is improved, but quality assurance issues arise due to volatility under high vacuum conditions

Engineering Contradiction:

Improveelectrical conductivityVSAvoidquality assurance

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The organic compound serves as a stable intermediary that prevents caesium volatility issues during vacuum processing. By depositing caesium atoms on the organic compound rather than handling pure caesium, the organic matrix stabilizes the caesium and prevents its evaporation under high vacuum conditions, ensuring consistent doping levels and manufacturing quality.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the physical state and chemical environment of caesium from metallic form to atomic form deposited on organic compounds. This parameter change transforms caesium from a volatile, reactive metal into a stable configuration that can be precisely controlled during vacuum deposition, improving manufacturing precision and quality assurance.

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If alternative dopants like lithium and metal complexes are used, then handling stability is improved, but conductivity and operational voltage optimization are limited

Engineering Contradiction:

Improvehandling stabilityVSAvoidconductivity

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The organic compound acts as an intermediary that enables the use of caesium atoms with improved handling stability compared to metallic caesium, while still achieving the high conductivity benefits. This intermediary approach allows access to caesium's superior electrical properties without the handling difficulties, and the method can be extended to other electropositive metals for optimized device performance.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 approach results in OLEDs with lower operational voltage and higher efficiency, enabling the use of thicker electron transporting layers and improved charge carrier generation, overcoming the limitations of previous dopants in terms of stability and performance.

Implementation Method 1

A semiconducting material comprising (i) in substantially elemental form, an electropositive element... and (ii) at least one first compound... wherein the first compound is a substantially covalent compound

Methodology Applied

Scientific EffectElectron transfer: Redox Reactions

Implementation Method 2

using a process that involves co-evaporation and codeposition under reduced pressure

Methodology Applied

Scientific EffectEvaporation: Evaporation

Implementation Method 3

co-evaporation and codeposition under reduced pressure

Methodology Applied

Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Data Source

PatentEP3109919B1N-doped semiconducting material comprising polar matrix and metal dopant

Publication Date: 2021.06.23 NOVALED GMBH

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Figure 3

AI summary

The invention relates to a semiconducting material comprising (i) in substantially elemental form, an electropositive element selected from alkaline metals, alkaline earth metals, rare earth metals, and transition metals, and (ii) at least one first compound which is a compound comprising at least one polar group selected from phosphine oxide group or diazole group; a process for manufacturing the semiconducting material; an electronic device comprising a cathode, an anode and the semiconducting material.