Formation of J-aggregates of mixed merocyanine dyes in Langmuir–Blodgett films

The formation and stability of J-aggregates of a [6Me-DS]1−x[DO]x mixed dye system in Langmuir–Blodgett films have been investigated using absorption and photoluminescence measurements. The variations of the spectral weights of the J-aggregate and DO monomer bands with DO content x allowed us to find that there exist two different regions: phase separation and solid solution. For 0 ≤ x ≤ 0.3, J-aggregates are formed from 6Me-DS molecules, and DO molecules exist as a monomer. In the range 0.4 ≤ x ≤ 0.8, J-aggregates are stably formed from both 6Me-DS and DO molecules. We have also found that the quantum efficiency of the J-aggregate emission for x = 0.6–0.7 is higher than for the pure 6Me-DS dye system.