Figure 1
From: Room temperature triplet state spectroscopy of organic semiconductors

Competing rates of deactivation of a photo-excited organic molecule.
Lowest excited states in both singlet (S1) and triplet (T1) manifold are shown, which are energetically split by their exchange splitting ΔEST. Singlets are created upon photo-excitation from the ground state (S0) and can deactivate through fluorescence [F] and non-radiative recombination [nr,F] or transfer to the triplet state via intersystem crossing [ISC]. Competing rates for the triplet excitons are phosphorescence [P] and non-radiative recombination [nr,P]. Additionally displayed are the two criteria (i) and (ii) to obtain phosphorescence.