Organic Light-Emitting Layer Structure for Triplet Energy Conversion
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Solution Overview
Problem
Current light-emitting elements, particularly those using fluorescent compounds, face challenges in achieving high emission efficiency and low driving voltage due to inefficient conversion of triplet excitation energy into light, and require materials with favorable carrier-transport properties to lower driving voltage and power consumption.
Innovation Solution
A light-emitting element structure incorporating a first organic compound that converts triplet excitation energy into light, a second organic compound with a benzofuropyrimidine or benzothienopyrimidine skeleton for improved electron transport, and a third compound for efficient singlet excitation energy conversion, forming an exciplex that enhances energy transfer and emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fluorescent compound is used in a light-emitting element, then the element can be manufactured with greater stability, but the emission efficiency is reduced due to inefficient conversion of triplet excitation energy into light
Solution Approach 1:
The patent introduces a thermally activated delayed fluorescent (TADF) material as an intermediary substance in the light-emitting layer. This TADF material acts as a mediator that accepts triplet excitation energy from the fluorescent compound through reverse intersystem crossing, then converts it to singlet excitation energy, which is subsequently transferred to the fluorescent compound for light emission. This intermediary mechanism enables efficient triplet energy conversion while maintaining fluorescent compound stability.
2Loss of energy
If a phosphorescent compound is used to convert triplet excitation energy into light, then the emission efficiency is improved, but the compound stability deteriorates particularly for blue light emission
Solution Approach 1:
The patent employs a TADF material with a short-lived triplet excited state that rapidly undergoes reverse intersystem crossing to singlet state. This short-lived intermediary state efficiently transfers energy to the fluorescent compound before degradation can occur, achieving high triplet energy conversion without the stability issues of long-lived phosphorescent compounds, particularly for blue light emission.
3Device complexity
If conventional materials are used in the light-emitting layer, then the device structure remains simple, but the driving voltage remains high due to insufficient carrier-transport properties
Solution Approach 1:
The patent creates a composite light-emitting layer by combining three functional materials: a fluorescent compound (for stable light emission), a TADF material (for triplet energy conversion), and a host material with excellent carrier-transport properties (for lowering driving voltage). This composite structure integrates multiple functions within a single layer, achieving low driving voltage through improved carrier transport while maintaining structural simplicity.
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 proposed structure achieves high emission efficiency, low driving voltage, and reliable operation by efficiently converting triplet excitation energy into light, thereby improving the performance of light-emitting elements and reducing power consumption.
Implementation Method 1
The first organic compound has a function of converting triplet excitation energy into light
Implementation Method 2
In a thermally activated delayed fluorescent material, a singlet excited state is generated from a triplet excited state by reverse intersystem crossing, and then the singlet excitation energy is converted into light
Implementation Method 3
singlet excitation energy of the thermally activated delayed fluorescent material is transferred to the fluorescent compound and light emission is obtained from the fluorescent compound
Implementation Method 4
research and development have been extensively conducted on light-emitting elements utilizing electroluminescence (EL). By application of a voltage between the electrodes of this element, light is emitted from the light-emitting substance
Data Source
AI summary
An object is to provide a light-emitting element with high emission efficiency. The light-emitting element contains first to third organic compounds. The first organic compound has a function of converting triplet excitation energy into light. The second organic compound has a benzofuropyrimidine skeleton or a benzothienopyrimidine skeleton. The third organic compound is a fluorescent compound. Light emitted from the light-emitting element is light emitted from the third organic compound that receives excitation energy from the first organic compound or from an exciplex formed by the first and second organic compounds.