Two-Coordinate Metal Amide Complexes for Saturated OLED Emission
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Solution Overview
Problem
Current organic light-emitting diodes (OLEDs) face challenges in achieving saturated colors for full-color displays, particularly in red, green, and blue emissions, due to limitations in thermally activated delayed fluorescence (TADF) compounds, which require efficient luminescence and high intersystem crossing rates.
Innovation Solution
Development of two-coordinate (carbene)Metal(amide) complexes, specifically with Cu(I), Ag(I), and Au(I) metals, O, S, or Se as ligands, and amide ligands, which facilitate thermally activated delayed fluorescence through spatial separation of highest occupied and lowest unoccupied molecular orbitals, enhancing emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional TADF compounds are used in OLEDs, then emission efficiency can be achieved, but color saturation is insufficient due to limitations in intersystem crossing rates
Solution Approach 1:
The patent changes the chemical composition parameters by introducing heavy metal ions (Cu(I), Ag(I), Au(I)) into the TADF compound structure. This parameter change modifies the electronic structure and enhances intersystem crossing rates through spin-orbit coupling, thereby achieving both high color saturation and maintained emission efficiency simultaneously
Solution Approach 2:
The patent creates composite materials by combining organic TADF ligands with inorganic heavy metal ions to form coordination complexes. This composite structure leverages the benefits of both organic materials (molecular design flexibility) and inorganic materials (heavy atom effect for enhanced ISC), resolving the contradiction between color saturation and emission efficiency
2Illumination intensity
If iridium-based phosphors are used to achieve saturated colors, then color saturation improves, but device complexity and cost increase
Solution Approach 1:
The patent replaces expensive, complex iridium-based phosphors with cheaper copper(I), silver(I), or gold(I) coordination complexes that have shorter lifetimes but sufficient performance for display applications. This substitution reduces material cost and simplifies device structure while maintaining saturated color emission
Solution Approach 2:
The patent changes the emitter material parameters from conventional TADF compounds to heavy metal coordination complexes, which have different photophysical properties including enhanced spin-orbit coupling. This parameter change achieves saturated colors without requiring the complex molecular structures of iridium phosphors, thereby reducing device complexity
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 proposed compounds exhibit high emission efficiency and luminescence rates, overcoming previous TADF limitations by modulating non-radiative decay rates through steric bulk and ligand orientation, leading to improved color saturation and performance in OLEDs.
Implementation Method 1
These two-coordinate complexes emit via thermally activated delayed fluorescence (TADF), with efficient luminescence in microsecond to sub-microsecond time scale
Implementation Method 2
a small singlet-triplet splitting energy (ΔEST) favors intersystem crossing (ISC) from the lowest energy triplet (T1) to singlet (S1) states
Implementation Method 3
The high ISC rate is due to the strong spin orbital coupling (SOC) (Marian, et al., Annu. Rev. Phys. Chem. 72(1) (2021) 617-640; Liidtke, et al., Physical Chemistry Chemical Physics 22(41) (2020) 23530-23544) provided by the central metal ion
Implementation Method 4
OLEDs make use of thin organic films that emit light when voltage is applied across the device
Data Source
AI summary
Provided are compounds of Formula (I). Also provided are formulations comprising these compounds. Further provided are OLEDs and related consumer products that utilize these compounds.