TADF Compound for OLED High Efficiency Low Cost
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Solution Overview
Problem
Current organic light-emitting diode (OLED) materials, particularly fluorescent and phosphorescent materials, face limitations in internal quantum yield and stability due to high production costs and efficiency drops under high electric current density, while thermally activated delayed fluorescence (TADF) materials are scarce and require development for efficient OLED devices.
Innovation Solution
A novel electroluminescent compound with TADF properties is introduced, featuring a specific chemical structure that includes electron donor and acceptor groups, allowing for efficient reverse intersystem crossing and high luminescence efficiency, which can be used as a light-emitting material in OLED devices, offering cost-effectiveness and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If phosphorescent materials are used in OLED, then internal quantum yield can reach 100%, but production cost increases due to heavy metal complexes
Solution Approach 1:
The patent replaces expensive phosphorescent materials containing heavy metals (Ir, Pt, Os, Re, Ru) with organic TADF materials that are cheaper and do not require rare metal elements. The TADF materials achieve comparable internal quantum yield through thermal activation of delayed fluorescence without the need for costly heavy metal complexes, making large-scale production economically viable
Solution Approach 2:
The patent modifies the energy level parameters of the organic compounds to enable reverse intersystem crossing (RISC) from triplet excited state to singlet excited state. By carefully designing the energy gap between S1 and T1 states to be small enough for thermal activation, the material achieves high internal quantum yield through TADF mechanism, replacing the heavy metal-dependent phosphorescence pathway
2Loss of energy
If phosphorescent materials are used in OLED, then internal quantum yield can reach 100%, but device stability deteriorates under high electric current density
Solution Approach 1:
The patent replaces phosphorescent materials with organic TADF materials that do not contain heavy metals, thereby eliminating the efficiency roll-off problem that occurs under high current density. The organic-based TADF materials maintain stable performance and do not exhibit the substantial efficiency fall characteristic of phosphorescent materials under high electric current conditions
3Ease of manufacture
If fluorescent materials are used in OLED, then production cost is low, but external quantum efficiency does not exceed 5%
Solution Approach 1:
The patent changes the emission mechanism from conventional fluorescence to thermally activated delayed fluorescence by modifying the energy level parameters. The TADF materials maintain the cost advantage of organic compounds while achieving high external quantum efficiency (up to 20% or higher) by utilizing both singlet and triplet excitons through reverse intersystem crossing, overcoming the 5% efficiency limit of traditional fluorescent materials
4Loss of energy
If TADF materials are developed for OLED, then production cost is reduced and efficiency is improved, but the number of available TADF materials is scarce
Solution Approach 1:
The patent employs a modular molecular design strategy where the TADF core structure can be combined with various electron donor (D) and electron acceptor (A) groups. This segmentation approach allows systematic exploration of different molecular configurations (with m donors and n acceptors where m+n≤6), enabling the development of multiple TADF materials with different emission colors and properties from a unified structural framework
Solution Approach 2:
The patent creates a universal TADF material platform based on the general formula (I) that can serve multiple functions. By varying the electron donor and acceptor groups, the same core structure can be adapted for different applications including red, green, and blue light-emitting materials, as well as host and guest materials, thereby expanding the versatility and availability of TADF materials for various OLED applications
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 compound achieves high luminescence efficiency and improved external quantum efficiency in OLED devices, reducing production costs and maintaining stability under high electric current, while enabling the use of TADF materials as red, green, or blue light-emitting materials.
Implementation Method 1
when an energy level difference between the singlet excited state and the triplet excited state is relatively small, a reverse intersystem crossing (RISC) may occur among the molecules, and the excitons are converted from T1 state to S1 state by absorbing the ambient heat
Implementation Method 2
a reverse intersystem crossing (RISC) may occur among the molecules, and the excitons are converted from T1 state to S1 state by absorbing the ambient heat
Implementation Method 3
The compound having the TADF property according to the present disclosure can be used as a light-emitting material of a light-emitting layer in an organic light-emitting display device
Data Source
AI summary
The present disclosure provides a compound having property of thermally activated delayed fluorescence (TADF) and a display device. The compound has a structure represented by Formula (I), in which X is S, O, Se, or C; D is an electron donor, A is an electron acceptor; m is a number of the electron donor D, and the m electron donors D are the same or different; n is a number of the electron acceptor, and the n electron acceptors are the same or different, m and n are integers each independently selected from 1, 2, 3, 4 or 5, and m+n≤6. The above compound provides a high luminescence efficiency. The organic light-emitting display device has advantages of improved luminescence efficiency, lower cost and long service life by using the above compound as a light-emitting material, a host material, or a guest material.