Copper(I) Complexes Singlet Harvesting OLED Emitters
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Solution Overview
Problem
Current OLED technologies face inefficiencies due to the use of expensive and toxic triplet emitters, particularly those based on precious metals like iridium, platinum, and gold, which have high spin-orbit coupling, leading to long emission lifetimes, saturation effects, and undesirable chemical reactivity, limiting their luminous efficacy and service life.
Innovation Solution
Development of copper(I) complexes with specific electronic structures that exhibit short emission lifetimes, high emission quantum yields, and solubility in various solvents, utilizing a singlet harvesting mechanism to overcome the limitations of traditional triplet emitters by adjusting the singlet-triplet energy difference and incorporating sterically demanding substituents to stabilize the molecular structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If triplet emitters based on precious metals (iridium, platinum, gold) are used in OLEDs, then high spin-orbit coupling and phosphorescence emission are achieved, but emission lifetime becomes excessively long, causing saturation effects and reduced service life
Solution Approach 1:
The patent changes the fundamental emission mechanism parameter from triplet phosphorescence to singlet fluorescence by designing copper(I) complexes with specific ligand fields that stabilize the singlet excited state. This parameter change in the emission pathway directly reduces emission lifetime from milliseconds to microseconds while maintaining high quantum yields through optimized singlet-triplet energy gaps
Solution Approach 2:
The invention replaces expensive precious metal triplet emitters with inexpensive copper(I) complexes that utilize singlet emission. The copper complexes achieve short emission lifetimes (microsecond range) inherently through their electronic structure, eliminating the saturation problems associated with long-lived triplet states while being cost-effective
2Use of energy by moving object
If triplet emitters with high spin-orbit coupling are used, then all excitons can be exploited for light emission (100% internal quantum yield), but the emission lifetime becomes too long leading to saturation effects
Solution Approach 1:
The patent optimizes the singlet-triplet energy gap parameter in copper(I) complexes to enable efficient singlet emission while preventing excessive triplet population. By tuning this energy parameter, the system achieves high internal quantum yield through singlet harvesting mechanism, avoiding the saturation effects that plague long-lived triplet emitters
Solution Approach 2:
The invention employs short-lived singlet emitters based on copper(I) complexes instead of long-lived triplet emitters. The microsecond-scale emission lifetime of singlet states enables high productivity and luminous efficacy by preventing saturation effects, while the use of copper replaces expensive precious metals
3Use of energy by moving object
If conventional triplet emitters are used, then high efficiency is achieved, but the materials are expensive and toxic, limiting cost-effectiveness and ecological compatibility
Solution Approach 1:
The patent replaces toxic and expensive precious metal triplet emitters with inexpensive, non-toxic copper(I) complexes. The copper complexes achieve comparable or superior emission efficiency through singlet emission mechanisms, while being environmentally friendly and cost-effective for large-scale OLED manufacturing
Solution Approach 2:
The invention changes the emission mechanism parameter from triplet phosphorescence to singlet fluorescence in copper(I) complexes. This parameter change enables high efficiency emission while using abundant, non-toxic copper instead of rare precious metals, resolving the contradiction between performance and ecological compatibility
4Object-affected harmful factors
If copper(I) complexes are used to replace precious metals, then cost and toxicity are reduced, but emission quantum yields were previously low due to geometry changes after excitation
Solution Approach 1:
The patent optimizes the ligand field parameters around copper(I) to stabilize the geometry in the excited state, preventing the Jahn-Teller distortion that previously caused low quantum yields. By tuning the ligand field strength and geometry, high emission quantum yields are achieved while maintaining the advantages of copper-based complexes
Solution Approach 2:
The invention uses composite ligand systems around copper(I) centers, combining different ligand types (e.g., N-heterocyclic carbenes with aromatic substituents) to create stable complexes with high quantum yields. The composite ligand structure provides both geometric stabilization and enhanced emission properties
5Duration of action of stationary object
If copper(I) complexes are designed with short emission lifetimes, then saturation effects are reduced and service life is extended, but roll-off behavior must be optimized
Solution Approach 1:
The patent optimizes the copper(I) complex parameters to achieve microsecond-scale emission lifetimes that balance service life extension with roll-off minimization. By precisely tuning the ligand field and molecular structure, the emission lifetime is optimized to be short enough to prevent saturation but long enough to maintain high luminous efficacy across operating conditions
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 copper(I) complexes achieve significantly improved luminous efficacy, reduced roll-off behavior, and extended service life by enabling efficient light emission and thermal repopulation of singlet states, while being cost-effective and less toxic, thus addressing the limitations of previous emitter materials.
Implementation Method 1
utilizing a singlet harvesting mechanism to overcome the limitations of traditional triplet emitters by adjusting the singlet-triplet energy difference
Implementation Method 2
enabling efficient light emission and thermal repopulation of singlet states
Implementation Method 3
with a singlet structure proposed here for the first time for Cu(I) complexes, which emit light from the singlet state to the ground state
Data Source
Figure 1
Figure 2a~2b
Figure 3
AI summary
The invention relates to neutral mononuclear copper (I) complexes for emitting light and with a structure according to formula (A) in which: M represents: Cu(I); LnL represents: a single, negatively charged, bidentate ligand; NnN represents: a diimine ligand (substituted with R and FG), in particular a substituted 2,2'-bipyridine derivative (bpy) or a substituted 1,10-phenanthroline derivative (phen); R represents: at least one sterically demanding substituent for preventing the planarisation of the complex in the excited state; FG = functional group, and represents: at least one second substituent for increasing solubility in organic solvents. The substituent can also be used for electron transport or alternatively for hole transport, said functional group being bound to the diimine ligands either directly or by means of suitable bridges; and the copper (I) complex: having a ?E(S1-T1) value of less than 2500 cm-1 between the lowest excited singlet state (S1) and the triplet state (T1) which lies below; having an emission lifespan of at most 20 µs; having an emission quantum yield of greater than 40%, and a solubility of at least 1 g/L in organic solvents, in particular polar organic hydrocarbons such as acetone, methyl ethyl ketone, benzene, toluene, chlorobenzene, dichlorobenzene, dichloromethane, chloroform, dichloroethane, tetrachloroethylene, alcohols, acetonitrile or water.