OLED Mixture Composition for Pinhole-Free Film Formation

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Solution Overview

Problem

The development of printed organic light-emitting diodes (OLEDs) is hindered by the poor film-forming properties and short lifetime of small molecular materials, which crystallize during heating, leading to decreased performance and limited commercial viability.

Innovation Solution

A mixture of three or more organic compounds with molecular weight differences less than 160 Dalton, each with optoelectronic functions, is used to create a stable formulation for solution processing, enabling pinhole-free and uniform film formation and maintaining amorphous morphology.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If small molecular materials are used in OLED preparation, then excellent device performance is achieved, but poor film forming property and crystallization during heating occur

Engineering Contradiction:

Improvedevice performanceVSAvoidfilm stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent uses a composite material system consisting of small molecular OLED materials combined with specific polymers (polycarbonate or polyacrylonitrile) as matrix materials. This composite approach allows the small molecular materials to maintain their excellent optoelectronic performance while the polymer matrix provides structural stability, prevents crystallization during heating, and ensures proper film forming properties through solution processing.

Inventive Principle:

Principle #40Composite materials

2Reliability

If vacuum evaporation method is used, then OLED performance is improved, but material utilization rate decreases and production cost increases

Engineering Contradiction:

ImproveOLED performanceVSAvoidmaterial utilization rate

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The patent replaces the vacuum evaporation method (a physical vapor deposition process) with a solution processing method. This substitution allows the OLED materials to be deposited from liquid solutions through techniques like spin coating or printing, significantly improving material utilization rate while maintaining device performance. The solution processing eliminates the need for high vacuum environments and reduces material waste.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Loss of substance

If solution processing is used for small molecular materials, then material utilization improves, but film forming property deteriorates due to crystallization

Engineering Contradiction:

Improvematerial utilization rateVSAvoidfilm forming quality

Core Design Contradiction:

Loss of substanceVSManufacturing precision

Solution Approach 1:

The patent changes the processing parameters by selecting specific polymer matrix materials (polycarbonate or polyacrylonitrile) with appropriate glass transition temperatures and molecular weights. These parameter changes prevent crystallization of the small molecular materials during solution processing and subsequent heating, ensuring uniform film formation while maintaining high material utilization rates.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS10978642B2Mixture, composition and organic electronic device

Publication Date: 2021.04.13 GUANGZHOU CHINARAY OPTOELECTRONICS MATERIALS LTD

AI summary

A mixture consists of three or more organic compounds, wherein the molecular weight difference of any two organic compounds is less than 160 Dalton. In the mixture, the molar percentage of each organic compound is not less than 3% and not more than 90%, and the organic compounds all have at least one same or similar photoelectronic function.