TADF Nitrogen Heterocyclic Compounds for OLED Efficiency
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Solution Overview
Problem
Current organic light-emitting diode (OLED) technologies using fluorescent materials are limited by low external efficiency due to the utilization of only 25% of singlet excitons, while phosphorescent materials, although more efficient, are costly and face challenges with blue phosphorescence efficiency and lifespan.
Innovation Solution
Development of nitrogen-containing heterocyclic compounds with specific structural formulas that exhibit thermally activated delayed fluorescence (TADF) properties, enabling the use of both singlet and triplet excitons for enhanced light-emitting efficiency without rare metal elements, and their integration into OLED structures as light-emitting layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If fluorescent materials are used in the light-emitting layer, then the device structure is simple and material cost is low, but the external efficiency is limited to 25% due to utilization of only singlet excitons
Solution Approach 1:
The patent changes the energy level parameters of the light-emitting materials by designing specific molecular structures with appropriate HOMO-LUMO gaps and energy level alignments. This enables efficient charge injection and exciton generation while maintaining ease of manufacturing with conventional OLED processes
Solution Approach 2:
The patent employs composite material systems combining different organic compounds in the light-emitting layer, host-guest doping systems, and multi-layer structures with complementary materials. This composite approach achieves high external efficiency through synergistic effects while maintaining manufacturing simplicity
2Productivity
If phosphorescent materials are used in the light-emitting layer, then the quantum efficiency reaches 100% by utilizing both singlet and triplet excitons, but the material cost is high due to rare metal elements and blue phosphorescence has efficiency and lifespan issues
Solution Approach 1:
The patent replaces expensive phosphorescent materials containing rare metals with conventional fluorescent organic compounds that are cheaper and easier to manufacture. Although fluorescent materials have shorter exciton lifetimes, the patent compensates through optimized energy level design and device structures to achieve comparable overall efficiency without the high material costs
Solution Approach 2:
The patent extracts and eliminates the need for rare metal elements (iridium, platinum) from the light-emitting layer by using purely organic fluorescent materials. This extraction approach maintains quantum efficiency through alternative mechanisms while dramatically reducing material cost and improving device stability
3Productivity
If blue phosphorescence materials are used, then the light-emitting efficiency is improved, but the lifespan is reduced due to stability issues of phosphorescent compounds
Solution Approach 1:
The patent uses stable fluorescent organic materials instead of unstable phosphorescent materials, accepting the shorter exciton lifetime as a trade-off for dramatically improved device lifespan and reliability. The overall light-emitting efficiency is maintained through optimized device structures and charge transport layers
Solution Approach 2:
The patent optimizes the energy level parameters, charge carrier mobility, and exciton diffusion lengths of the fluorescent materials to compensate for the shorter exciton lifetime. This parameter optimization achieves high light-emitting efficiency while maintaining the superior stability and lifespan of fluorescent materials over phosphorescent alternatives
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 nitrogen-containing heterocyclic compounds achieve comparable light-emitting efficiency to phosphorescent materials while reducing material costs, offering improved performance and longevity, particularly for blue phosphorescence, and are applicable in various organic photoelectric devices.
Implementation Method 1
the band gap value of the S1 state and the T1 state of the TADF material is relatively small; and the lifespan of the T1 excitons of the TADF material is relatively long. Under a certain temperature condition, the T1 excitons may have a reverse intersystem crossing (RISC) to achieve the T1→S1 process
Implementation Method 2
Under a certain temperature condition, the T1 excitons may have a reverse intersystem crossing (RISC) to achieve the T1→S1 process
Implementation Method 3
the fluorescent materials are only able to use 25% of singlet excitons (S1), which can be back to the ground state S0 by a radiative transition
Data Source
AI summary
A nitrogen-containing heterocyclic compound having a general formula (I) and an organic photoelectric apparatus are provided. The compound of general formula (I) is:wherein A1 to A4 are independently selected from a hydrogen atom, a function group having a general formula (II); A1 to A4 include at least one function group having the general formula (II); R1 and R2 are independently selected from one of hydrogen, deuterium, C1-30 alkyl group, C6-30 aromatic group and C2-30 heterocyclic aromatic group; Y1 and Y2 are independently selected from substituted or non-substituted C and N,the general formula (II) being:wherein X is selected from one of oxyl group (—O—), sulfhydryl group (—S—), substituted or non-substituted imino group, substituted or non-substituted methylene group, and substituted or non-substituted silicylene group; and R3 to R10 are independently selected from one of hydrogen, deuterium, C1-30 alkyl group, C6-30 aromatic group, and C2-30 heterocyclic aromatic group.