Computational discovery of OLED materials

Most of the electrically generated excitons in organic light emitting diodes (OLEDs) are in a non-radiative triplet state. In thermally activated delayed fluorescence (TADF) chromophores triplet excitons can be converted into bright singlet excitons via reverse intersystem crossing (RISC). This requires the energy barrier between the singlet and triplet states to be very low or, ideally, completely absent. In addition, it is desirable for the color of OLED chromophores to be sharp and tunable. Computer simulations can accelerate the discovery of materials with these properties. Time dependent density functional theory (TDDFT) is the method of choice for predicting the excited-state properties of chromophores. However, its reliability depends strongly on the exchange-correlation functional used. We benchmark the performance of TDDFT methods [Phys. Rev. Research 4, 033147 (2022)] and demonstrate their applications for the discovery of new TADF chromophores [Electronic Structure 5, 014010 (2023)] and graphitic carbon nitride flakes with inverted singlet-triplet gaps [J. Phys. Chem. Lett. 14, 10910 (2023)].