In situ energy-dispersive X-ray reflectivity measurements of structural changes in thin films for organic electroluminescent devices

An energy-dispersive grazing incident X-ray reflectivity (ED-GIXR) measuring system employing white X-rays and a solid-state X-ray detector (SSD) was first utilized to follow the structural changes occurring in organic EL multilayered films during annealing processes. The data on density, layer thickness and interface roughness obtained for N,N′ -diphenyl-N,N′ -bis(3-methylphenyl)-(1,1′ -biphenyl) -4,4′ diamine (TPD) film and tri(8-hydroxyquinoline) aluminum (Alq3)/TPD films on Si wafer substrates suggested that the instability of TPD films induces a lower stability of Alq3 film by mutual interaction at higher temperature ranges above the glass transition temperature of TPD.