OLED Emitter Energy Cascade for Exciton Utilization
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Solution Overview
Problem
Conventional organic light emitting diodes (OLEDs) face limitations in driving voltage, luminous efficiency, color purity, and luminous lifespan, particularly due to the short lifespan of phosphorescent materials and the inability to effectively utilize triplet excitons in luminescence processes.
Innovation Solution
An OLED structure incorporating a first and second compound with specific energy level relationships and structures, allowing for efficient transfer and utilization of both singlet and triplet excitons through delayed fluorescent materials, which enhances luminous efficiency and extends lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phosphorescent materials are used to improve luminous efficiency, then luminous efficiency is improved, but luminous lifespan becomes too short for commercial application
Solution Approach 1:
The patent changes the energy level parameters of the emitting materials by selecting compounds with specific HOMO energy levels where the difference between the two compounds is within 0.1-0.5 eV. This parameter optimization enables efficient exciton transfer while maintaining material stability and long lifespan, resolving the contradiction between luminous efficiency and lifespan
Solution Approach 2:
The patent uses a composite emitting material layer comprising two different compounds (first compound from Formula 1 or 1′ and second compound from Formula 4 or 4′) with complementary properties. The first compound has higher HOMO energy level and the second has lower HOMO energy level, creating a energy cascade that enables efficient triplet exciton transfer while both materials contribute to long operational lifespan
2Duration of action of moving object
If conventional fluorescent materials are used, then luminous lifespan is extended, but luminous efficiency is low because only singlet excitons are utilized
Solution Approach 1:
The patent introduces the second compound as an intermediary material with lower HOMO energy level that acts as a mediator for triplet exciton transfer. The triplet excitons generated in the first compound are transferred to the second compound, which then transfers them to the emitting material, enabling efficient utilization of triplet excitons while maintaining fluorescent material lifespan
Solution Approach 2:
The patent replaces the direct luminescence mechanism of conventional fluorescent materials with an indirect energy transfer mechanism. Instead of fluorescent materials directly utilizing triplet excitons (which they cannot), the system uses energy transfer through the two-compound system to convert triplet excitons into singlet excitons that can emit light, achieving high efficiency without sacrificing lifespan
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 OLED design reduces driving voltage, improves luminous efficiency, and extends the luminous lifespan by effectively utilizing both singlet and triplet excitons, leading to improved color purity and quantum efficiency.
Implementation Method 1
the at least one emitting material layer includes a first compound and a second compound... allowing for efficient transfer and utilization of both singlet and triplet excitons through delayed fluorescent materials
Implementation Method 2
when electrical charges are injected into an emitting material layer between an electron injection electrode (i.e., cathode) and a hole injection electrode (i.e., anode), electrical charges are recombined to form excitons, and then emit light as the recombined excitons are shifted to a stable ground state
Data Source
AI summary
An organic light emitting diode (OLED) including at least one emitting material layer (EML) disposed between two electrodes and comprising a first compound including a fused ring of boron and oxygen as a nuclear atom and a second compound including a fused ring of born and nitrogen as a nuclear atom and an organic light emitting device including the OLED is disclosed. The first compound and the second compound may be the same emitting material layer or adjacently disposed emitting material layers. The OLED can lower its driving voltage and improve its luminous efficiency using the first and second compounds with adjusting their energy levels.