Sub-picosecond fluorescence dynamics of organic light-emitting diode tris(8-hydroxyquinoline) metal complexes

Abstract For a few complexes belonging to a new class of organic light-emitting diodes (OLED), namely Al(III)– and Ga(III)– tris -8-hydroxyquinoline (Alq 3 and Gaq 3 ), femtosecond fluorescence up-conversion measurements are reported. The fluorescence decays contain picosecond components when the complexes are dissolved in liquid solution. The fast components are not found in the time-resolved fluorescence of the complexes doped in an inert host crystal. The results in liquid solution are characteristic of a dynamic Stokes shift due to the solvation in a ligand-localized excited state. Furthermore, from the temporal behavior of the total fluorescence intensity it is concluded that, concomitant with solvation, adiabatic electron transfer takes place.

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