Singlet Exciton Diffusion in Vacuum-Evaporated Films of Amine-Based Materials as Studied by Photocurrent and Photoluminescence Quenching Methods

The singlet exciton diffusion lengths are determined by the photoconductivity as well as the luminescence surface quenching technique, in vacuum-evaporated layers of (4,4,4-tris(N-(3-methylphenyl)-N-phenylylamino) triphenylamine) (m-MTDATA), 4,4,4-tris[2-naphthyl(phenyl)amino] triphenylamine (2TNATA), and N,N-diphenyl-N,N-bis(3-methylphenyl)-[1,1-biphenyl]-4,4-diamine (TPD) which are frequently used for fabrication of electroluminescent and photovoltaic devices. The values are found to be as high as (30 +/- 10)nm in 2TNATA and m-MTDATA, as well as (46 +/- 9)nm in TPD films. The corresponding singlet diffusion coefficients of the range between 1x10(-3) and 1x10(-2)cm(2)s(-1), according to a comprehensive study undertaken, are assigned to a sizable electronic coupling induced by strong interactions of intra- and inter-molecular origin in the investigated materials.