Modeling TADF in organic emitters requires a careful consideration of the environment and going beyond the Franck–Condon approximation

Twisted: Efficient thermally-activated delayed fluorescence (TADF) of organic emitters emerges from a delicate interplay of nuclear relaxation, dielectric stabilization and post Franck–Condon effects along the donor–acceptor twisting coordinate.

Effect of temperature on rate of the spin-forbidden transition in uracil and thymine

The intersystem crossing rates of uracil and thymine molecules in interaction with the heat bath were studied by means of the ab initio methods. The rates were calculated employing the time-dependent approach based on the correlation function. The normal modes of the singlet and triplet electronic states were related by the Duschinsky transformation. The correlation function was calculated using the Condon approximation for the spin-orbit matrix element and harmonic approximation for the nuclear motion. The excess vibrational energy in the initial singlet excited electronic state decreases the rate of the triplet formation in uracil and thymine. This decrease is more pronounced for uracil. Also, it was found that the change of the adiabatic energy gap can significantly modify the rate of the triplet formation.