Dissecting non-radiative decay in donor-functionalized radicals with a mode-resolved model

Area of Science:

• Materials Science
• Organic Electronics
• Computational Chemistry

Background:

• Donor-functionalized radicals, based on the poly-chlorinated trityl moiety, are promising emitters for advanced optoelectronic devices.
• The efficiency of these emitters is significantly influenced by the non-radiative decay pathways of their charge-transfer (CT) states.
• Understanding and controlling this decay is critical for optimizing molecular design and device performance.

Purpose of the Study:

• To develop a mode-resolved theoretical model that correlates non-radiative decay rates with specific molecular structural features and vibrational modes.
• To investigate the impact of electronic structure calculations, particularly the role of exact exchange in density functional theory (DFT), on modeling CT state decay.
• To elucidate the mechanisms behind the suppression of non-radiative decay in specific molecular architectures, such as those with perpendicular donor-acceptor arrangements.

Main Methods:

• Development and application of a mode-resolved theoretical model.
• Utilizing density functional modeling with a focus on exact exchange, solvation, and anharmonic effects.
• Performing sensitivity analyses on the Franck-Condon weighted density of states (FCWDOS) to identify contributions from individual vibrational modes.

Main Results:

• The study highlights the critical role of exact exchange in DFT for accurately modeling CT state decay.
• It demonstrates that perpendicular donor-acceptor arrangements in radical emitters suppress non-radiative decay.
• This suppression is attributed to reduced coupling between the promoting vibrational mode and the CT exciton, along with diminished anharmonic contributions.

Conclusions:

• A comprehensive understanding of non-radiative decay mechanisms in donor-functionalized radicals is achieved through a mode-resolved vibrational analysis.
• The findings provide crucial insights for the rational molecular design of efficient emitters for next-generation optoelectronics.
• The study underscores the importance of considering vibrational dynamics, electronic structure details (exact exchange), and anharmonicity for predicting and controlling emitter performance.