Radiation Emitting Device Fluorescent Phosphorescent Layer Segmentation

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Solution Overview

Problem

Radiation emitting devices have a low yield of emissive radiation relative to the voltage applied, primarily due to the inefficiency in converting energy from both singlet and triplet excited states into emitted radiation.

Innovation Solution

A radiation emitting device is designed with a layer sequence comprising a first charge carrier transporting layer with a fluorescent substance and a second charge carrier transporting layer with a phosphorescent substance, where the second layer is largely free of first charge carriers, allowing for energy transfer and increased radiation yield by utilizing both singlet and triplet excited states through the inclusion of phosphorescent substances.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a conventional radiation emitting device uses only fluorescent substances, then the device structure is simple, but the radiation yield is low because triplet excited states cannot be efficiently converted to emitted radiation

Engineering Contradiction:

Improveradiation yieldVSAvoidlayer structure complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The device is divided into multiple functional layers: a first charge carrier transporting layer containing fluorescent substance, a second charge carrier transporting layer containing phosphorescent substance, and intermediate layers for energy transfer. This segmentation allows separate optimization of fluorescent and phosphorescent emission pathways, enabling efficient conversion of both singlet and triplet excited states to radiation while maintaining manageable structural complexity through functional specialization.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The device employs composite material structure combining fluorescent and phosphorescent substances in distinct layers with energy transfer interfaces. The first charge carrier transporting layer contains fluorescent substance for singlet state emission, while the second charge carrier transporting layer contains phosphorescent substance for triplet state emission. Energy transfer layers facilitate coupling between these materials, creating a composite system that achieves high radiation yield by utilizing both emission mechanisms synergistically.

Inventive Principle:

Principle #40Composite materials

2Use of energy by moving object

If the second charge carrier transporting layer contains both first and second charge carriers, then charge transport is efficient, but recombination occurs which prevents effective energy transfer to phosphorescent substance

Engineering Contradiction:

Improveenergy transfer efficiency to phosphorescent substanceVSAvoidcharge transport efficiency

Core Design Contradiction:

Use of energy by moving objectVSProductivity

Solution Approach 1:

The charge transport function is segmented into two distinct layers: the first charge carrier transporting layer handles first charge carriers (holes or electrons), while the second charge carrier transporting layer handles second charge carriers (electrons or holes). This spatial separation prevents recombination of opposite charge carriers within the phosphorescent layer, ensuring that energy transfer to phosphorescent substance occurs through triplet exciton diffusion rather than charge carrier recombination, thereby maintaining both energy transfer efficiency and charge transport efficiency.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Energy transfer layers are introduced as intermediaries between the charge carrier transporting layers and the phosphorescent substance. These intermediate layers facilitate efficient energy transfer from triplet excitons to the phosphorescent dopant while preventing direct charge carrier recombination. The intermediary structure enables decoupling of charge transport and energy transfer processes, allowing each to be optimized independently for maximum efficiency.

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 configuration significantly enhances the radiation yield by converting a higher proportion of energy into emitted radiation, particularly from triplet states, thereby improving the device's efficiency and spectral coverage.

Implementation Method 1

a first charge carrier transporting layer, which comprises a fluorescent substance

Methodology Applied

Scientific EffectFluorescence: Fluorescence

Implementation Method 2

a second charge carrier transporting layer, which contains a phosphorescent substance

Methodology Applied

Scientific EffectPhosphorescence: Phosphorescence

Implementation Method 3

the energy for the excitation of the phosphorescent substance has to be transferred from the first charge carrier transporting layer into the second charge carrier transporting layer

Methodology Applied

Scientific EffectEnergy transfer:

Data Source

PatentUS8610114B2Radiation emitting device

Publication Date: 2013.12.17 AMS OSRAM INT GMBH

AI summary

A radiation emitting device comprising a first electrode, which emits first charge carriers having a first charge during operation, a first charge carrier transporting layer, which comprises a fluorescent substance, a second charge carrier transporting layer, which contains a phosphorescent substance, and a second electrode, which emits second charge carriers having a second charge during operation, wherein during operation the second charge carrier transporting layer is largely free of first charge carriers.