Aggregation-Induced Intersystem Crossing: Rational Design for Phosphorescence Manipulation.

Area of Science:

• Physical Chemistry
• Materials Science
• Organic Electronics

Background:

• Organic phosphorescence is crucial for energy and life science applications.
• Slow intersystem crossing (ISC) in organic molecules limits phosphorescence efficiency due to small spin-orbit couplings (SOC) and large singlet-triplet energy gaps (ΔE_S-T).
• Molecular aggregation is a strategy to enhance phosphorescent properties.

Purpose of the Study:

• To investigate the impact of molecular aggregation on the luminescence properties of the π-conjugated benzophenone luminophore 1-dibenzo[b,d]thiophen-2-yl(phenyl)methanone (BDBT).
• To explore the 'aggregation-induced intersystem crossing' (AI-ISC) mechanism.
• To analyze the effect of functional groups on phosphorescence efficiency.

Main Methods:

• Theoretical investigation using density functional theory (DFT) and time-dependent DFT.
• Analysis of molecular aggregation effects on energy splitting and SOC.
• Introduction of electron donating and withdrawing functional groups to tailor phosphorescence.

Main Results:

• Molecular aggregation significantly alters energy splitting and SOC, leading to changes in ISC rates via the AI-ISC mechanism.
• Functional groups effectively influence SOC and energy gaps, modulating phosphorescence efficiency.
• Systems with donating functional groups exhibit faster ISC rates; dimers show optimal luminescence due to favorable SOC and ΔE_S-T.

Conclusions:

• The AI-ISC mechanism provides a viable route for enhancing organic phosphorescence.
• Group functionalization, combined with AI-ISC, offers a practical platform for optimizing phosphorescent materials.
• Tailoring molecular aggregation and functional groups is key to designing efficient phosphorescent organic molecules.