Temperature Change in Structure of Bilayers of ALQ/TPD-Doped Polycarbonate Films for Organic Electroluminescent Devices

Abstract

The change of surface and interface in bilayers of Alq (Tris-(8-hydroxyquinoline) aluminum) / TPD (N,N′-diphenyl-N,N′-bis-(3-methylphenyl)-(1,1′-biphenyl)-4,4′-diamine)-doped polycarbonate (PC) films for organic electroluminescent devices was characterized by atomic force microscopy (AFM), SEM, and fluorescence microscopy, in the temperature range from R.T. to 250 °C under the air. As single layer films, the dip-coated TPD-doped PC film on indium-tin oxide (ITO)-coated glass and the vapor-deposited Alq films on various substrates showed good thermal stability compared with the vapor-deposited TPD film itself. However, in the bilayered structure of Alq / TPD-doped PC films, the Alq film as the overlaying layer was deteriorated readily, which was accelerated with increasing temperature and TPD concentration in the TPD-doped PC film.