OLED Emissive Layer Host-Guest Delayed Fluorescence
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Solution Overview
Problem
Current organic light-emitting diodes (OLEDs) face challenges in achieving high efficiency and color accuracy, particularly in producing saturated colors like red, green, and blue, due to limitations in emissive materials and device configurations.
Innovation Solution
A compound with a specific structure, according to Formula 1 and Formula 2, is used in the emissive layer of OLEDs, incorporating donor and acceptor groups to enhance light emission through delayed fluorescence, allowing for improved color rendition and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If traditional fluorescent OLED materials are used, then the device structure is simple, but the external quantum efficiency is limited to below 25% due to loss of triplet states
Solution Approach 1:
The patent introduces a host-guest system where the host material acts as an intermediary to facilitate triplet state utilization. The host absorbs energy from excitons and transfers it to the guest emitter, enabling triplet state harvesting through delayed fluorescence without requiring complex phosphorescent multi-layer structures. This mediator approach resolves the contradiction by achieving high efficiency through a relatively simple emissive layer configuration.
Solution Approach 2:
The patent modifies key parameters of the emissive system by selecting host and guest materials with specific energy level alignments, triplet energy values, and photophysical properties. By optimizing these parameters—such as ensuring the host has higher triplet energy than the guest and appropriate singlet-triplet energy gaps—the system achieves over 25% external quantum efficiency through delayed fluorescence while maintaining a simple device structure.
2Use of energy by moving object
If phosphorescent materials are used to harvest triplet states, then external quantum efficiency can exceed 25%, but the device requires complex multi-layer configurations and precise energy level alignment
Solution Approach 1:
The host material serves as a mediator that simplifies the triplet state harvesting process. Instead of requiring direct phosphorescent emission from the guest, the host absorbs triplet energy and facilitates delayed fluorescence emission. This intermediary mechanism achieves efficient triplet state utilization without the need for complex phosphorescent multi-layer device configurations.
Solution Approach 2:
The emissive layer is designed to be self-sufficient by incorporating both host and guest materials with complementary photophysical properties that enable autonomous triplet state harvesting and delayed fluorescence emission. The system self-regulates energy transfer and emission processes through proper material selection, eliminating the need for additional complex device layers or external controls.
3Manufacturing precision
If conventional fluorescent emitters are used, then the manufacturing process is simple, but the color saturation and accuracy cannot meet industry standards for saturated red, green, and blue pixels
Solution Approach 1:
The patent applies local quality by selecting specific guest emitters with tailored photophysical properties for each color channel (red, green, blue). Each guest material is chosen to emit at a specific wavelength with high purity, enabling saturated colors that meet industry standards. The host-guest system allows independent optimization of each color's emission characteristics without affecting the manufacturing simplicity of the overall device.
Solution Approach 2:
The emissive layer uses composite host-guest material systems where the host provides the structural and energy transfer framework while the guest provides the specific color emission. This composite approach combines the manufacturing simplicity of conventional fluorescent OLEDs with the color accuracy of specialized emitters, achieving both ease of manufacture and high color saturation through material composition rather than structural complexity.
4Productivity
If the emissive layer uses simple fluorescent mechanisms, then the device structure is straightforward, but the internal quantum efficiency cannot exceed 25% due to non-radiative triplet state decay
Solution Approach 1:
The host material acts as an intermediary that captures triplet states through energy transfer from excitons and converts them into delayed fluorescence. This mediator mechanism enables the emissive layer to utilize both singlet and triplet excitons productively, achieving internal quantum efficiency exceeding 25% while maintaining a relatively straightforward emissive layer composition with only host and guest components.
Solution Approach 2:
The delayed fluorescence mechanism ensures continuous light emission by converting triplet states that would otherwise decay non-radiatively into productive photon-emitting events. The host-guest system maintains continuous useful action by systematically transferring energy from excitons to hosts to guests, ensuring that both singlet and triplet excitons contribute to light emission, thereby achieving high productivity without complex device structures.
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 these compounds in OLEDs results in enhanced external quantum efficiency and color performance, exceeding the limits of traditional fluorescent OLEDs by harnessing triplet states for delayed fluorescence, leading to improved device efficiency and color accuracy.
Implementation Method 1
incorporating donor and acceptor groups to enhance light emission through delayed fluorescence
Implementation Method 2
OLEDs make use of thin organic films that emit light when voltage is applied across the device
Data Source
AI summary
A compound having the structure of Formula 1,as well as, a first device and a formulation including the same are disclosed. In the structure of Formula 1:R5 isand(a) at least one of R1-R4 isor (b) R1 isIn addition, R1, R2, R3, R4, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, B1, B2, B3, B4, B5, B6, B7, B8, B9, B10, Y1, Y2, Y3, Y4, Y5, Y6, Y7, Y8, Z1, Z2, Z3, Z4, Z5, Z6, Z7, and Z8, are each independently selected from a variety of substituents, where adjacent A, B, Y, and Z groups are, optionally, joined to form a fused ring structure. Finally, X includes an acceptor group selected from —CmF2m+1, —SimF2m+1, —NCO, —NCS, —OCN, —SCN, —OCmF2m+1, and —SCmF2m+1.