Efficient Prediction of Singlet–Triplet Gaps in Delayed Fluorescence Emitters Using Kohn–Sham Orbital Energies

Accurate prediction of singlet–triplet gaps (STGs)
is crucial
for designing inverted singlet–triplet (INVEST) and thermally
activated delayed fluorescence (TADF) emitters, which are key to next-generation
organic light-emitting diodes. However, the widely used time-dependent
density functional theory (TDDFT) fails to reliably predict STGs with
mainstream functional approximations, while more accurate wave function
methods are computationally too expensive. In this work, we demonstrate
that quasiparticle energy density functional theory (QE-DFT) provides
a highly efficient and accurate alternative for predicting STGs, calculating
them directly from Kohn–Sham orbital energy differences. Using
the B3LYP functional, QE-DFT achieves a mean absolute error of 0.06
eV across diverse STG sets containing 233 INVEST and TADF molecules,
significantly outperforming TDDFT with conventional functional approximations.
Furthermore, its low computational cost makes QE-DFT especially suitable
for high-throughput virtual screening. This work highlights QE-DFT
as a promising tool for accelerating the discovery of new INVEST and
TADF emitters.