Modeling Molecular Emitters in Organic Light-Emitting Diodes with the Quantum Mechanical Bespoke Force Field

Combined molecular dynamics (MD)
and quantum mechanics (QM) simulation
procedures have gained popularity in modeling the spectral properties
of functional organic molecules. However, the potential energy surfaces
used to propagate long-time scale dynamics in these simulations are
typically described using general, transferable force fields designed
for organic molecules in their electronic ground states. These force
fields do not typically include spectroscopic data in their training,
and importantly, there is no general protocol for including changes
in geometry or intermolecular interactions with the environment that
may occur upon electronic excitation. In this work, we show that parameters
tailored for thermally activated delayed fluorescence (TADF) emitters
used in organic light-emitting diodes (OLEDs), in both their ground
and electronically excited states, can be readily derived from a small
number of QM calculations using the QUBEKit (QUantum mechanical BEspoke
toolKit) software and improve the overall accuracy of these simulations.