Organic Light-Emitting Device Mixed Layer Triplet Exciton Harvesting

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Solution Overview

Problem

Organic light emitting devices face inefficiencies due to the utilization of only singlet excitons, with triplet excitons generated by electron-hole recombination remaining unused, leading to reduced efficiency.

Innovation Solution

Incorporating a mixed layer with hole transfer materials and electron transfer materials to form a charge transfer complex, which reuses triplet excitons by adjusting the energy levels and spin states, allowing for the utilization of both singlet and triplet excitons for enhanced light emission efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a conventional organic light emitting device uses only singlet excitons for light emission, then the device structure is simple, but the efficiency is low because triplet excitons remain unused

Engineering Contradiction:

Improvelight emission efficiencyVSAvoiddevice structure

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The device is segmented into distinct functional layers: a light emitting layer that generates excitons and a mixed layer that facilitates triplet exciton utilization. This segmentation allows each layer to perform its specific function optimally, with the mixed layer containing both hole transfer and electron transfer materials to enable triplet exciton harvesting and conversion to singlet excitons for light emission

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The mixed layer uses composite materials comprising both hole transfer materials and electron transfer materials in combination. This composite structure enables the layer to perform multiple functions: transporting holes, transporting electrons, and facilitating triplet exciton to singlet exciton conversion, thereby resolving the contradiction between efficiency improvement and structural simplicity

Inventive Principle:

Principle #40Composite materials

2Reliability

If triplet excitons are utilized through a mixed layer, then quantum efficiency improves, but the device requires additional materials and layer configuration

Engineering Contradiction:

Improvequantum efficiencyVSAvoidlayer configuration

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The mixed layer is designed with multi-functionality, serving as both a charge transport layer and a triplet exciton harvesting layer. By incorporating both hole transfer and electron transfer materials, the layer universally handles multiple tasks: charge injection, charge transport, and exciton management, thereby improving quantum efficiency without requiring separate dedicated layers for each function

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Use of energy by moving object

If a mixed layer is added to improve efficiency, then power efficiency improves, but the device structure becomes more complex

Engineering Contradiction:

Improvepower efficiencyVSAvoidstructure

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The mixed layer converts the previously harmful or wasted triplet excitons into useful singlet excitons that can emit light. By incorporating both hole transfer and electron transfer materials, the layer facilitates the conversion of triplet excitons (which would otherwise be lost) into singlet excitons, thereby converting a waste product into a beneficial light-emitting species and improving power efficiency

Inventive Principle:

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

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 improves light emission efficiency by maximizing the use of triplet excitons, resulting in higher quantum efficiency and lower driving voltage, with the mixed layer being strategically positioned adjacent to the light emitting layer to facilitate energy transfer and exciton reuse.

Implementation Method 1

a mixed layer including one or more hole transfer materials and one or more electron transfer materials

Methodology Applied

Scientific EffectCharge transfer complex formation:

Implementation Method 2

the mixed layer can increase the efficiency of the organic light emitting device by reusing the triplet excitons generated in the light emitting layer, and using a charge transfer complex generated within the mixed layer

Methodology Applied

Scientific EffectEnergy transfer:

Implementation Method 3

The principle of the organic light emission phenomenon is as follows. When an organic material layer is placed between an anode and a cathode, if voltage is applied to the specific organic molecule through two electrodes, electrons and holes from the cathode and the anode, respectively, flow into the organic material layer. The electrons and the holes injected into the organic material layer are recombined to form excitons, and these excitons fall back to the ground state and emit light.

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS9508949B2Organic light-emitting device

Publication Date: 2016.11.29 LG DISPLAY CO LTD

AI summary

An organic light emitting device includes a first electrode, a second electrode, and two or more organic material layers provided between the first electrode and the second electrode. The organic material layer includes a light emitting layer, and a mixed layer including one or more hole transfer materials and one or more electron transfer materials.