Fig. 5: Excited-state pathways.
From: Efficient near-infrared organic light-emitting diodes with emission from spin doublet excitons
a, Calculated energetic landscape for a range of 17 molecular complexes of MADN and TTM-TPA. The filled black circles represent the average excitation energies and vertical bars quantify the standard deviation: T1 = 2.02 ± 0.02 eV; S1 = 3.25 ± 0.04 eV; D1 = 1.93 ± 0.08 eV; D2 = 2.79 ± 0.03 eV; inter-2CT = 1.89 ± 0.12 eV. The inset shows the molecular conformation of CP1. The computed average lifetime of τSD to the D2 and D1 states is 23 ps and 9 ps, respectively. Energy transfer from T1 to D1 occurs in a superexchange-like mechanism mediated by the presence of low-lying inter-2CT states, with a computed overall lifetime τTD spanning from tens of nanoseconds to tens of picoseconds. b, Scheme of exciton pathways and their approximate rates. Triplet excitons form either an overall doublet (2[D0–T1]) or quartet (4[D0–T1]) encounter pair when adjacent to a radical site. Reversible energy transfer occurs in the doublet configuration, whereas quartet pairs separate during triplet diffusion.
