On the radiative lifetime, quantum yield and fluorescence decay of Alq in thin films

The fluorescence decay of tris(8-hydroxyquinolinato)aluminium(III) (Alq) in thin films and organic solvents was studied as a function of temperature. The variation of the nonradiative rate constant of Alq with temperature follows the Arrhenius equation and the activation energy is 0.074 eV for crystalline film and 0.039 eV for amorphous film. Similarly, the activation energies of Alq in frozen organic solvents were determined to be 0.051 eV (DMSO) and 0.049 eV (ethanol). The radiative lifetime of Alq was determined to be 156 +/- 19 ns using the linear correlation of the inverse fluorescence lifetime at 77 K in several organic solvents with the square of the refractive index. The maximum internal fluorescence quantum yield for a thin crystalline and amorphous film of Alq are estimated to be 0.36 and 0.21, respectively.