Exciton dynamics in an aromatic diamine at the interface with 8-hydroxyquinoline aluminum

Exciton dynamics parameters such as diffusion length, l(d), and surface quenching velocity, upsilon, in an amorphous film of an aromatic diamine (TPD) have been measured utilizing both the quenching effect exerted on its fluorescence by a thin layer of 8-hydroxyquinoline aluminum (Alq(3)) deposited on the film as well as the exciton detector layer radiative emission itself. It is found that l(d) = (30 +/- 10) nm and upsilon = (2 +/- 1) x 10(3) cm/s. Using independent data on the intrinsic lifetime in TPD yields the diffusion coefficient of excitons D = (5 +/- 1) x 10(-3) cm(2)/s. The results are discussed in connection with the operation mechanism of the double-layer electroluminescent structure based on the TPD/Alq(3) junction.