TADF Organic EL Compound for Triplet Exciton Utilization
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Solution Overview
Problem
Existing organic electroluminescence (EL) devices have limitations in internal quantum efficiency due to the reliance on singlet excitons, with a maximum efficiency of 25%, and there is a need to efficiently utilize triplet excitons for improved performance.
Innovation Solution
A compound represented by formula (1) is introduced, which can be used to form an organic-electroluminescence-device material, organic electroluminescence device, and electronic device. This compound allows for the improvement of organic EL device performance by incorporating specific structural elements that facilitate the use of triplet excitons through thermally activated delayed fluorescence (TADF) mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fluorescent organic EL device uses only singlet excitons for light emission, then the device structure is simple, but the internal quantum efficiency is limited to 25%
Solution Approach 1:
The patent modifies the energy level parameters of the organic compound by introducing specific molecular structures with donor and acceptor moieties. This changes the singlet-triplet energy gap (ΔEST) to enable efficient reverse intersystem crossing, allowing triplet excitons to be converted to singlet excitons for light emission, thereby achieving internal quantum efficiency exceeding 25% while maintaining device structural simplicity
Solution Approach 2:
The patent converts the previously harmful or wasted triplet excitons (which constituted 75% of generated excitons but did not contribute to light emission) into useful light-emitting singlet excitons through thermally activated delayed fluorescence. This transforms the waste energy pathway into a beneficial contribution to device efficiency, achieving internal quantum efficiency greater than 25%
2Productivity
If triplet excitons are utilized through TADF mechanism, then internal quantum efficiency improves beyond 25%, but the device requires specific molecular structure design
Solution Approach 1:
The patent employs composite molecular structures combining electron-donor moieties and electron-acceptor moieties within a single organic compound. This composite structure creates the necessary conditions for TADF by establishing appropriate energy level separations and spatial distribution of HOMO and LUMO orbitals, enabling efficient triplet-to-singlet conversion while maintaining reasonable molecular design complexity
Solution Approach 2:
The patent divides the organic compound into functional segments: a donor moiety and an acceptor moiety. This segmentation allows independent optimization of each moiety's properties while ensuring their combination produces the desired TADF effect. The modular approach simplifies the design process by allowing systematic selection and combination of known donor and acceptor building blocks
3Duration of action of stationary object
If conventional fluorescent materials are used, then the device has shorter lifetime, but achieving high efficiency requires complex triplet exciton management
Solution Approach 1:
The patent enables the organic compound to self-manage triplet excitons through intrinsic TADF properties. The molecular structure is designed to automatically facilitate reverse intersystem crossing from triplet to singlet state via thermal activation, eliminating the need for external complex triplet exciton management systems. This self-service mechanism simultaneously achieves high internal quantum efficiency and extended device lifetime
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 the compound in organic EL devices enhances performance by potentially increasing internal quantum efficiency beyond the 25% limit, improving luminance, reducing drive voltage, and extending the device's lifetime.
Implementation Method 1
a highly efficient fluorescent organic EL device using thermally activated delayed fluorescence (hereinafter, sometimes simply referred to as "delayed fluorescence") has been proposed and studied
Implementation Method 2
A TADF (Thermally Activated Delayed Fluorescence) mechanism uses such a phenomenon that inverse intersystem crossing from triplet excitons to singlet excitons thermally occurs
Implementation Method 3
When a voltage is applied to an organic electroluminescence device (hereinafter, occasionally referred to as "organic EL device"), holes are injected from an anode and electrons are injected from a cathode into an emitting layer. The injected electrons and holes are recombined in the emitting layer to form excitons.
Data Source
AI summary
A compound is represented by a formula (1). In the formula (1), at least one combination of adjacent two or more of R1 to R17 are mutually bonded to form a ring represented by a formula (2), in which RX1 to RX4 and R1 to R17 are each independently a hydrogen atom, a substituent or the like,