The Best of Both Worlds: ΔDFT Describes Multiresonance TADF Emitters with Wave-Function Accuracy at...

Area of Science:

• Computational materials science
• Organic electronics
• Photophysics

Background:

• Multiresonance thermally activated delayed fluorescence (MR-TADF) emitters are crucial for advanced OLED technology due to their efficient light emission.
• Accurate computational modeling of singlet-triplet (ST) energy gaps and fluorescence energies in MR-TADF materials is essential but challenging.
• Traditional methods like time-dependent density functional theory (TD-DFT) have limitations, while accurate coupled-cluster (CC) methods are computationally expensive.

Purpose of the Study:

• To introduce and validate a state-specific ΔDFT approach based on unrestricted Kohn-Sham (ΔUKS) calculations for modeling MR-TADF emitters.
• To assess the performance of ΔUKS against established methods like coupled-cluster (CC2) for predicting key photophysical properties.
• To demonstrate the broad applicability of ΔUKS for various TADF emitters, including those with inverted energy gaps.

Main Methods:

• Utilized a state-specific ΔDFT approach based on unrestricted Kohn-Sham (ΔUKS) calculations.
• Benchmarked the ΔUKS method against experimental data for a diverse set of 35 MR-TADF emitters.
• Employed a tuned range-separated LC-ωPBE functional in conjunction with the ΔUKS approach.

Main Results:

• The ΔUKS method achieved a mean absolute deviation (MAD) of 0.03 eV for predicting experimental ST gaps, comparable to or better than CC2.
• ΔUKS demonstrated high accuracy in predicting fluorescence energies and ST gaps for a wide range of TADF emitters.
• The method proved effective even for molecules with inverted singlet-triplet energy gaps (INVEST).

Conclusions:

• The state-specific ΔUKS approach offers a computationally efficient and accurate method for modeling MR-TADF emitters.
• This versatile method provides a valuable tool for the rational design and development of next-generation organic electronic materials.
• ΔUKS represents a significant advancement, combining accuracy with reduced computational cost for organic electronics research.