Multinuclear Metal Complexes for Short Emission Lifetimes
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Solution Overview
Problem
Phosphorescent triplet emitters in OLEDs have long emission lifetimes leading to saturation effects and efficiency reduction, while existing materials for OSCs lack high light absorption and exciton diffusion lengths.
Innovation Solution
Development of mono- or polynuclear metal complexes with small singlet-triplet energy separations, facilitating singlet harvesting and high absorption coefficients, which are used in OLEDs and OSCs to achieve short emission lifetimes and efficient light conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phosphorescent triplet emitters are used in OLEDs to achieve high light yield through triplet harvesting, then the internal quantum yield can reach 100%, but the emission lifetime becomes relatively long (microseconds) causing saturation effects and efficiency reduction at increasing current densities
Solution Approach 1:
The patent applies parameter changes by modifying the energy gap between singlet and triplet states (ΔE) to be very small (less than 0.3 eV). This parameter change enables thermal reoccupation of the singlet state from the triplet state at room temperature, creating a dual emission pathway that significantly shortens the emission lifetime while maintaining high internal quantum yield through triplet harvesting
Solution Approach 2:
The patent introduces the singlet state as an intermediary between the triplet state and the ground state. By enabling thermal reoccupation of the singlet state from the triplet state, it creates a fast decay pathway that mediates the transition, allowing the system to benefit from both triplet harvesting (high quantum yield) and short emission lifetime
2Use of energy by moving object
If conventional absorber materials are used in organic solar cells, then the device structure is simple, but the absorption coefficients and exciton diffusion lengths are insufficient for efficient solar energy conversion
Solution Approach 1:
The patent employs composite materials by combining metal complexes with specific ligand systems to create absorber materials that exhibit both high absorption coefficients and long exciton diffusion lengths. The composite structure of metal centers coordinated with organic ligands provides enhanced optoelectronic properties while maintaining compatibility with standard OLED device architectures
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 complexes achieve significantly reduced emission lifetimes and high emission quantum yields in OLEDs, and enhanced light absorption and exciton dissociation in OSCs, addressing efficiency and absorption limitations in prior art.
Implementation Method 1
This process is controlled by the Boltzmann distribution in accordance with equation (1). The intensity ratio is then given by Int(S1→S0)/Int(T1→S0)=k(S1)/k(T1)exp(−ΔE/kBT)
Implementation Method 2
The T1 state is occupied by the already known effects of triplet harvesting, and the usual T1→S0 phosphorescence results
Implementation Method 3
if the singlet state, which is excited at the same time and is energetically above the triplet state, relaxes completely into the triplet state (intersystem crossing)
Data Source
AI summary
The invention relates to the use of a multinuclear metal or transition metal complex in an organic electronic device, said complex having a small ΔE spacing, particularly between 50 cm−1 and 2000 cm−1, between the lowest triplet state and the singlet state that is higher and is achieved by thermal backfilling from the triplet. The invention further relates to the use of the strong absorptions of such multinuclear metal complexes, particularly in OSCs.