Thermally activated delayed fluorescence in luminescent cationic copper(i) complexes.

In this work, the photophysical characteristics of [Cu(N^N) 2 ] + and [Cu(N^N)(P^P)] + complexes were described. The concept of thermally activated delayed fluorescence (TADF) and its development throughout the years was also explained. The importance of Δ E (S 1 -T 1 ) and spin-orbital coupling (SOC) values on the TADF behavior of [Cu(N^N) 2 ] + and [Cu(N^N)(P^P)] + complexes is discussed. Examples of Δ E (S 1 -T 1 ) values reported in the literature were collected and some trends were proposed ( e.g. the effect of the substituents at the 2,9 positions of the phenanthroline ligand). Besides, the techniques (or calculation methods) used for determining Δ E (S 1 -T 1 ) values were described. The effect of SOC in TADF was also discussed, and examples of the determination of SOC values by DFT and TD-DFT calculations are provided. The last chapter covers the applications of [Cu(N^N) 2 ] + and [Cu(N^N)(P^P)] + TADF complexes and the challenges that are still needed to be addressed to ensure the industrial applications of these compounds.