Fig. 4. Schematic representation of excited-state transitions in [(DPEPhos)Cu(PyrTet)].

Shown are r, radiative transition (solid arrows); nr, nonradiative transition (oscillatory arrows). After excitation to the excited singlet state (I_a), intersystem crossing to the triplet state occurs (k_ISC). At sufficient temperature, the excitons are repopulated to the excited singlet state (k_RISC), and subsequently thermally activated delayed fluorescence occurs. k_S and k_T depict the rate constants from the excited singlet or triplet state, respectively.