Manipulating Multiple Resonance-Charge Transfer Hybrid Proportion for Developing Red Narrowband Thermally Activated...

Area of Science:

• Organic Chemistry
• Materials Science
• Photophysics

Background:

• Multiple resonance thermally activated delayed fluorescence (MR-TADF) materials offer 100% exciton utilization and narrowband emissions.
• Developing efficient red-emitting MR-TADF materials remains a significant challenge in optoelectronics.

Purpose of the Study:

• To theoretically investigate the design principles for red narrowband TADF materials.
• To explore the relationship between molecular structure and charge transfer properties in MR-TADF systems.
• To identify key molecular design strategies for achieving red emission.

Main Methods:

• Theoretical investigation using computational chemistry methods.
• Analysis of frontier molecular orbital (FMO) distributions and overlap.
• Correlation of molecular geometry, specifically dihedral angles, with charge transfer (CT) character.
• Systematic variation of MR cores and peripheral electron-donating units.

Main Results:

• The proportion of MR-charge transfer (CT) hybrid character in excited states is strongly linked to FMO/hole-electron overlap.
• Dihedral angles between MR cores and peripheral units are critical determinants of FMO/hole-electron overlap.
• Peripheral substituent electron-donating ability shows minimal impact on FMO/hole-electron overlap.
• Two novel molecular designs, c1-a and c2-a, exhibiting red narrowband emissions were identified.

Conclusions:

• Molecular design strategies focusing on dihedral angles are crucial for controlling MR-CT proportion and achieving red narrowband TADF emissions.
• These findings provide valuable insights for the rational design of advanced red-emitting optoelectronic materials.
• The study highlights the importance of theoretical investigations in guiding experimental efforts for novel material discovery.