title: Reliable Prediction with Tuned Range-Separated Functionals of the Singlet-Triplet Gap in Organic Emitters for Thermally Activated Delayed Fluorescence.
abstract: The thermally activated delayed fluorescence (TADF) mechanism has recently attracted significant interest in the field of organic light-emitting diodes (OLEDs). TADF relies on the presence of a very small energy gap between the lowest singlet and triplet excited states. Here, we demonstrate that time-dependent density functional theory in the Tamm-Dancoff approximation can be very successful in calculations of the lowest singlet and triplet excitation energies and the corresponding singlet-triplet gap when using nonempirically tuned range-separated functionals. Such functionals provide very good estimates in a series of 17 molecules used in TADF-based OLED devices with mean absolute deviations of 0.15 eV for the vertical singlet excitation energies and 0.09 eV [0.07 eV] for the adiabatic [vertical] singlet-triplet energy gaps as well as low relative errors and high correlation coefficients compared to the corresponding experimental values. They significantly outperform conventional functionals, a feature which is rationalized on the basis of the amount of exact-exchange included and the delocalization error. The present work provides a reliable theoretical tool for the prediction and development of novel TADF-based materials with low singlet-triplet energetic splittings.
authors.affiliation: Solar & Photovoltaics Engineering Research Center, Physical Science and Engineering Division, King Abdullah University of Science and Technology (KAUST) , Thuwal 23955-6900, Kingdom of Saudi Arabia.
authors.forename: Haitao
authors.initials: H
authors.lastname: Sun
authors.affiliation: Solar & Photovoltaics Engineering Research Center, Physical Science and Engineering Division, King Abdullah University of Science and Technology (KAUST) , Thuwal 23955-6900, Kingdom of Saudi Arabia.
authors.forename: Cheng
authors.initials: C
authors.lastname: Zhong
authors.affiliation: Solar & Photovoltaics Engineering Research Center, Physical Science and Engineering Division, King Abdullah University of Science and Technology (KAUST) , Thuwal 23955-6900, Kingdom of Saudi Arabia.
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Brédas