Organic Electroluminescent Element Using Heavy Atom Mediator
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Solution Overview
Problem
Current organic electroluminescent elements face challenges in achieving high emission efficiency, particularly for blue light, due to the shortening of molecular structure and reduced lifetime associated with increasing the energy gap, and existing techniques fail to balance emission wavelength and lifetime effectively.
Innovation Solution
Incorporating a thermally activated delayed fluorescent compound (TADF) with a heavy atom compound, such as iridium or platinum, to enhance intersystem crossing and utilize triplet excitons for improved fluorescence emission, thereby increasing emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the energy gap is increased to achieve shorter emission wavelength (blue light), then the emission wavelength is shortened, but the lifetime of the light-emitting element is shortened due to weakening of molecular structure
Solution Approach 1:
The patent introduces a heavy atom compound as an intermediary substance that mediates between the TADF compound and triplet excitons. The heavy atom compound facilitates intersystem crossing from triplet to singlet state through its heavy atom effect, enabling efficient utilization of triplet excitons without requiring high energy gap materials that would compromise molecular stability and lifetime
Solution Approach 2:
The patent changes the emission mechanism parameter from conventional fluorescent or phosphorescent mechanisms to a TADF mechanism enhanced by heavy atom effect. By adjusting the energy gap parameter ΔE ST to 0.01 eV or less and utilizing the heavy atom effect to enhance intersystem crossing rate, the system achieves high emission efficiency without needing to increase the energy gap to unrealistic levels, thereby maintaining molecular structure stability
2Reliability
If conventional fluorescent materials are used, then the molecular structure remains stable, but the emission efficiency is limited because only singlet excitons contribute to light emission
Solution Approach 1:
The heavy atom compound serves as an intermediary that enables triplet excitons to convert to singlet excitons through enhanced intersystem crossing. This mediator allows the system to overcome the fundamental limitation of fluorescent materials by providing a pathway for triplet exciton utilization without changing the basic fluorescent emission mechanism
Solution Approach 2:
The patent converts the previously harmful or wasted triplet excitons (which normally decay non-radiatively in fluorescent materials) into beneficial light-emitting singlet excitons through the heavy atom effect. By introducing the heavy atom compound, the system transforms the 75% energy loss from triplet exciton decay into useful fluorescence emission
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 TADF compounds with heavy atom compounds in organic electroluminescent elements enhances fluorescence emission, leading to improved emission efficiency and extended lifetime, addressing the limitations of existing technologies.
Implementation Method 1
any of the organic layers contains a thermally activated delayed fluorescent compound and/or a heavy atom compound which exhibits an external heavy-atom effect of promoting the intersystem crossing of the thermally activated delayed fluorescent compound from the triplet excitation state to the singlet excitation state and enhancing fluorescence emission
Implementation Method 2
promoting the intersystem crossing of the thermally activated delayed fluorescent compound from the triplet excitation state to the singlet excitation state
Implementation Method 3
Fluorescence occurs by radiation deactivation (also referred to as 'radiation transition' or 'radiative deactivation') during transfer from the singlet excited state to the ground state
Implementation Method 4
Fluorescence occurs by radiation deactivation (also referred to as 'radiation transition' or 'radiative deactivation') during transfer from the singlet excited state to the ground state
Implementation Method 5
Organic electroluminescent (hereinafter referred to as 'EL') elements (also referred to as 'organic electroluminescence light emitting devices'), which are based on electroluminescence of organic materials
Data Source
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AI summary
The present invention addresses the problem of providing: an organic electroluminescent element which exhibits an enhanced light emitting efficiency; a lighting device and a display device, each of which is provided with said organic electroluminescent device; a light-emitting thin film; a light-emitting composition; and a light-emitting method. An organic electroluminescent element (10,101) which is provided with one pair of electrodes (105,107) and one or multiple organic layers (106) disposed therebetween and which is characterized in that both a compound which emits a thermally activated delayed fluorescence and a heavy atom compound are each contained in any of the organic layers (106), said heavy atom compound having an external heavy-atom effect of accelerating the intersystem crossing from the triplet excited state of the compound which emits a thermally activated delayed fluorescence to the singlet excited state thereof and thus enhancing the fluorescence.