Under vacuum (Figure , dashed lines), the intensity of this low-energy band increases significantly relative to the intensity of the S1 band, and clear peaks can now be observed in the steady-state PL spectra of all five emitters. The shape of the S1 band, meanwhile, is unaffected by the removal of oxygen, except in 6,10NICz, which is slightly narrower under vacuum. The onset of emission is identical in all cases under both aerated and deaerated conditions.