The family of thermally activated delayed fluorescence (TADF) dyes based on diarylamino-functionalized dicyanobenzenes, has been extensively applied in fields such as organic electronics and photoredox catalysis during the last decade. In the latter field, light excitation of the TADF-dye leads to a reactive excited state that can be quenched through electron or energy transfer, leading to reactivity that is otherwise absent in the ground state. Photocatalysts based on transition-metal complexes of e.g., Ir or Ru, or non-TADF organic dyes, feature emission from a pure excited state. In most cases, the reactive excited state is a triplet that occurs after absorption of light and inter-system crossing (ISC), because triplet states feature longer lifetimes that allow for bimolecular reactivity. TADF-dyes, however, are characterized by an excited-state system that, in its simplest form, has two excited states (a singlet and a triplet) that are close enough in energy such that, in addition to ISC, thermal population of the higher-energy singlet excited state from the triplet, known as reverse intersystem crossing (RISC), occurs readily at room temperature. After excitation, these compounds decay back to the ground-state in a biexponential manner according to equation 1 which can be interpreted as a prompt decay of the initially pure singlet excited state (with rate constant 𝑘 𝑝 ), and a slower delayed decay of an equilibrium state of singlet and triplet excited states (with rate constant 𝑘 𝑑 ), see Figure .