OLED Layer Composition with Doped Molecular Layers

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Solution Overview

Problem

Existing organic light-emitting diodes (OLEDs) face limitations in flexibility of construction and charge carrier injection, particularly due to the need for stable materials that are susceptible to oxygen and water, and the difficulty in achieving efficient electron injection without damaging the organic layers, which restricts the integration of multiple polymeric layers and efficient light production.

Innovation Solution

Incorporating at least one polymer layer and two molecular layers, with the molecular layers being doped with organic or inorganic dopants of molecular weight greater than 200 g/mole, to enhance flexibility and structurability, and using vacuum deposition to prevent solvent interactions and improve layer combinations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If stable contact materials such as barium or calcium are used to achieve efficient electron injection, then electron injection efficiency is improved, but the materials are attacked by oxygen and water reducing reliability

Engineering Contradiction:

Improvestability against oxygen and waterVSAvoidelectron injection efficiency

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

A molecular electron-transporting layer is introduced as an intermediary between the cathode and the emitting polymer layer. This layer mediates the electron injection process, allowing efficient charge carrier injection without requiring highly reactive contact materials like barium or calcium that are susceptible to oxygen and water attack.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the material parameters by using small molecule materials with specific energy levels and mobilities in the molecular layers. The molecular weight of dopants is controlled to be greater than 200 g/mole to optimize the balance between injection efficiency and stability.

Inventive Principle:

Principle #35Parameter changes

2Shape

If a sputter process is used to deposit transparent cover contacts, then transparent cathode structure is achieved, but organic materials are damaged reducing light production efficiency

Engineering Contradiction:

Improvetransparent cover contact structureVSAvoidsputter damage to organic layers

Core Design Contradiction:

ShapeVSObject-generated harmful factors

Solution Approach 1:

The molecular electron-transporting layer is deposited in advance before the transparent cover contact is applied. This preliminary layer serves as a protective barrier that shields the underlying organic emitting layers from damage during the subsequent sputtering process, while still allowing the cover contact to be deposited in a transparent configuration.

Inventive Principle:

Principle #10Preliminary action

3Adaptability or versatility

If multiple polymeric layers are applied to increase layer flexibility, then layer composition flexibility is improved, but solvent interactions attack substrate material limiting the number of layers

Engineering Contradiction:

Improvelayer composition flexibilityVSAvoidsolvent attack on substrate

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the physical state and deposition method by using vacuum deposition of small molecules instead of solution processing with solvents. This eliminates solvent-related substrate attack while maintaining the ability to create multiple layers with different functions through precise control of deposition parameters and material selection.

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

This approach allows for improved flexibility in layer composition, easier structurability without expensive shadow masks, and enhanced charge carrier injection efficiency, reducing operating voltage and increasing light production while maintaining stability against sputter damage.

Implementation Method 1

layers formed as a molecular layer consisting of vacuum-deposited small molecules

Methodology Applied

Scientific EffectVacuum deposition: Physical Vapour Deposition

Implementation Method 2

the molecular layer being doped with an organic or inorganic dopant

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentUS8263429B2Light-emitting component and process for its preparation

Publication Date: 2012.09.11 NOVALED GMBH

AI summary

A light-emitting component comprising organic layers and having several layers between a base contact and a cover contact, the corresponding process for its preparation. At least one polymer layer and two molecular layers are arranged, so that when the cover contact is a cathode, the layer adjacent to the cover contact is designed as an electron-transporting molecular layer and is doped with an organic or inorganic donor, the electron-transporting layer comprising a principal organic substance and a donor-type doping substance, the molecular weight of the dopant being more than 200 g/mole. When the cover contact is an anode, the layer adjacent to the cover contact is designed as a p-doped hole-transporting molecular layer and is doped with an organic or inorganic acceptor, the hole-transporting layer comprising a principal organic substance and an acceptor-like doping substance, the molecular weight of the dopant being more than 200 g/mole.