Bridged Bicyclic Compounds for OLED TADF Efficiency
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Solution Overview
Problem
Current organic light-emitting diodes (OLEDs) face inefficiencies in converting electrical charges to light due to the weak emissive nature of triplet states in purely organic materials, as they require forbidden spin transitions, while singlet states are more emissive with allowed transitions, necessitating materials that facilitate interconversion of triplet states into singlet states for enhanced luminance.
Innovation Solution
The development of bridged bicyclic compounds, such as iptycene-based structures, which exhibit extended singlet emission lifetimes and a reduced energy gap between singlet and triplet excited states, enabling thermally activated delayed fluorescence (TADF) and high photoluminescence efficiency, are used in OLEDs to facilitate the interconversion of triplet states into singlet states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If triplet states are used in organic light-emitting materials, then the quantum yield can be improved by utilizing all excited states, but the emission efficiency deteriorates because triplet states require forbidden spin transitions
Solution Approach 1:
The patent changes the energy parameter by reducing the energy gap between singlet and triplet excited states to less than 0.2 eV. This enables thermal energy at operating temperatures to facilitate spin-flip transitions from triplet to singlet states, allowing triplet excitons to contribute to light emission through delayed fluorescence while maintaining efficient radiative transitions
Solution Approach 2:
The patent implements a two-stage emission process: immediate fluorescence from singlet states followed by thermally activated delayed fluorescence from triplet states. This periodic action allows both singlet and triplet excitons to contribute to light emission at different time scales, achieving near-100% internal quantum efficiency
2Loss of energy
If singlet states are used for light emission, then the emission efficiency is improved with allowed radiative transitions, but the quantum yield deteriorates because not all excited states can be transformed into luminance
Solution Approach 1:
The patent introduces thermal energy as an intermediary that mediates the conversion between triplet and singlet states. The small energy gap (<0.2 eV) allows thermal activation to drive spin-flip transitions, enabling triplet excitons to be converted into singlet excitons that can then undergo efficient radiative decay to produce light
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
These bridged bicyclic compounds enhance the quantum yield and emission efficiency of OLEDs by prolonging singlet emission lifetimes and reducing the energy gap between excited states, leading to improved light generation and emission characteristics.
Implementation Method 1
exhibit extended singlet emission lifetimes and a reduced energy gap between singlet and triplet excited states, enabling thermally activated delayed fluorescence (TADF) and high photoluminescence efficiency
Implementation Method 2
the [2.2.Z] bridged bicyclic compound has a singlet emission lifetime that is at least about 10 times greater than a singlet emission lifetime of at least one of an isolated A, B, and C group
Data Source
AI summary
Embodiments described herein relate to compositions including bridged bicyclic compounds such as iptycene-based structures and extended iptycene structures. In some embodiments, the compositions may be useful in organic light-emitting diodes (OLEDs), organic photovoltaics, and other devices.