Quantum Dot-Emitter Composites for OLED Color Purity

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Solution Overview

Problem

Organic light emitting diodes (OLEDs) face challenges with broad emission spectra, leading to reduced color purity and energy loss due to their amorphous nature and infrared emission, which limits their color space and efficiency compared to inorganic LEDs.

Innovation Solution

A composition comprising quantum dots (QDs) and fluorescent small molecule compounds is used to achieve efficient energy transfer, enhancing color purity and reducing energy loss by narrowing the emission bands in electroluminescent devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If OLEDs use organic molecules and amorphous films for light emission, then device fabrication is simplified and flexibility is improved, but emission spectrum becomes broad leading to reduced color purity

Engineering Contradiction:

Improvedevice fabricationVSAvoidcolor purity

Core Design Contradiction:

Ease of manufactureVSIllumination intensity

Solution Approach 1:

The patent combines quantum dots (inorganic nanocrystals) with organic ligands to form composite material structures. These quantum dot-emitter composite layers integrate the narrow emission bands of QDs with the beneficial properties of organic materials, achieving both ease of fabrication and high color purity through the composite structure's unique optical properties

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent introduces quantum dots as localized emissive centers within the organic film matrix. Each quantum dot acts as a discrete nanoscale emitter with inherently narrow emission spectrum, while the surrounding organic material provides flexibility and processability. This local quality approach maintains overall device flexibility while creating localized regions of high color purity

Inventive Principle:

Principle #3Local quality

2Power

If OLEDs emit in infrared region above 680 nm, then total energy output increases, but human eye cannot see this light resulting in energy loss

Engineering Contradiction:

Improvetotal energy outputVSAvoidinfrared energy loss

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The patent utilizes quantum confinement effects in quantum dots to precisely control and tune the emission wavelength by changing particle size. By adjusting quantum dot dimensions, the emission spectrum is optimized to match the human visual response function, maximizing luminous efficiency and minimizing infrared energy loss while maintaining high power output in the visible range

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts the typically harmful non-radiative recombination and energy loss in organic OLEDs into beneficial narrow-band emission by incorporating quantum dots. The quantum dots' size-dependent optical properties allow conversion of input energy into visible light with minimal infrared loss, transforming energy inefficiency into high luminous efficiency

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Power

If phosphorescent dopants are incorporated to harvest triplet excitons and achieve 100% internal quantum efficiency, then emission intensity increases, but emission bands remain broad reducing color purity

Engineering Contradiction:

Improveemission intensityVSAvoidcolor purity

Core Design Contradiction:

PowerVSIllumination intensity

Solution Approach 1:

The patent merges the advantages of phosphorescent emitters (high internal quantum efficiency through triplet exciton harvesting) with quantum dots (narrow emission bands). The quantum dot-emitter hybrid structure combines phosphorescent dopants with quantum dots, where quantum dots provide the narrow emission spectrum while phosphorescent materials ensure efficient triplet exciton utilization, achieving both high emission intensity and high color purity

Inventive Principle:

Principle #5Merging (Combining)

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 use of QDs and fluorescent small molecule compounds in OLEDs improves color purity, enlarges the color space, and reduces energy loss, resulting in more efficient and effective light emission.

Implementation Method 1

efficient energy transfer

Methodology Applied

Scientific EffectEnergy transfer:

Implementation Method 2

quantum dots (QDs)... narrowing the emission bands

Methodology Applied

Scientific EffectQuantum confinement:

Implementation Method 3

fluorescent small molecule compounds

Methodology Applied

Scientific EffectFluorescence: Fluorescence

Data Source

PatentEP3309236B1Electroluminescent device comprising quantum dots and use of a formulation comprising quantum dots

Publication Date: 2019.11.27 MERCK PATENT GMBH

Figure 1

AI summary

A composition is provided, including one or more quantum dots and at least one organic emitter. Further, a formulation including the composition, a use of the formulation and a device comprising the composition or formulation is provided.