Stilbene Derivative Host Material for Blue Light Emission

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Solution Overview

Problem

The development of light emitting elements with blue or shorter wavelength emission faces challenges due to the lack of suitable electron transporting materials with large energy gaps, leading to inefficient excitation energy transfer and poor color purity.

Innovation Solution

A stilbene derivative with a large energy gap is introduced as a host material in the light emitting layer, preventing excitation energy from moving to the electron transport layer and allowing for efficient blue light emission with high color purity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If a light emitting substance with blue or shorter wavelength emission is used, then the emission wavelength is shortened, but the host material must have a very large energy gap which is difficult to find

Engineering Contradiction:

Improveemission wavelengthVSAvoidavailability of host material

Core Design Contradiction:

Illumination intensityVSAdaptability or versatility

Solution Approach 1:

The patent changes the energy gap parameter of the host material by introducing a specific stilbene derivative with a large energy gap (3.2 eV or more), enabling it to support blue and shorter wavelength emission while maintaining material availability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite system by combining the stilbene derivative host material with appropriate light emitting substances, achieving the required energy gap characteristics without relying on a single material

Inventive Principle:

Principle #40Composite materials

2Adaptability or versatility

If an electron transporting material with small energy gap is used, then the material is readily available, but excitation energy moves to the electron transport layer causing poor color purity

Engineering Contradiction:

Improveavailability of electron transporting materialVSAvoidcolor purity

Core Design Contradiction:

Adaptability or versatilityVSIllumination intensity

Solution Approach 1:

The stilbene derivative acts as an intermediary host material between the light emitting substance and the electron transport layer, preventing excitation energy from moving to the electron transport layer while maintaining efficient energy transfer to the light emitting substance

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the energy gap parameter of the host material to be larger than that of the electron transporting material, creating an energy barrier that prevents excitation energy from moving to the electron transport layer, thus maintaining color purity

Inventive Principle:

Principle #35Parameter changes

3Illumination intensity

If a host material with large energy gap is used for blue light emission, then color purity is improved, but the number of suitable materials is limited

Engineering Contradiction:

Improvecolor purityVSAvoidmaterial selection complexity

Core Design Contradiction:

Illumination intensityVSDevice complexity

Solution Approach 1:

The patent identifies and utilizes a specific parameter threshold (energy gap of 3.2 eV or more) for the host material, providing a clear guideline for material selection and simplifying the device design process

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent develops a composite material system using a stilbene derivative as the host, which can be combined with various light emitting substances to achieve different emission wavelengths while maintaining color purity

Inventive Principle:

Principle #40Composite materials

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

The stilbene derivative enables the creation of light emitting elements with improved emission efficiency and color purity, suitable for blue, red, and green light emissions, while also being applicable for violet to ultraviolet light emissions by acting as a host material.

Implementation Method 1

the host material needs to have a larger energy gap than the light emitting substance. This is an important requirement aiming at prevention of changes in light emission efficiency and light emission color due to excitation energy of an excited light emitting substance moving to the host material

Methodology Applied

Scientific EffectEnergy gap:

Implementation Method 2

aiming at improvement in light emission efficiency due to the excitation energy moving smoothly from the excited host material to the light emitting substance

Methodology Applied

Scientific EffectExcitation energy transfer:

Data Source

PatentUS7638663B2Stilbene derivative, light emitting element material, light emitting element, light emitting device and electronic appliance

Publication Date: 2009.12.29 SEMICON ENERGY LAB CO LTD

AI summary

An object of the present invention to provide a novel stilbene derivative having a large energy gap. In addition, it is another object of the present invention to provide a novel light emitting element material having a large energy gap which is suitable for a host material in a light emitting layer. Further in addition, it is another object of the present invention to provide a novel light emitting element material having a large energy gap and an electron transporting property. The present invention provides a stilbene derivative represented by a following general formula (3) and a light emitting element material including the stilbene derivative represented thereby:wherein, n is an integer of 0 or more and 2 or less and m is an integer of 1 or more and 2 or less.