The interfacial change of a vapor-deposited tris(8-hydroxyquinoline) aluminum complex (Alq 3 )/N,N -diphenyl-N,N -bis(3-methyl-phenyl)-(1,1 -biphenyl)-4,4 -dia mine (TPD) (Alq 3 TPD) bilayer and the surface morphology of the Alq 3 /TPD bilayer and the mixed single layers of co-deposited TPD and Alq 3 were characterized by fluorescence microscopy and spectroscopy, and atomic force and friction force microscopy in the range of temperature from room temperature to 80°C under air. In this study was found enhanced suppression of the crystallization of TPD in a molecularly dispersed system such as the co-deposited Alq 3 -TPD mixed film in comparison with the single-component TPD film. It was also found that the crystallization of Alq 3 in the interface of the bilayer or in the co-deposited single layer proceeded before the crystallization of TPD.