Phosphorescent organic light-emitting devices with in situ post-growth annealed organic layers

A comparative study of in situ post-growth annealing of organic layers before hole-blocking layer (HBL) or metal cathode deposition was conducted on tris-(phenyl-pyridyl)-iridium complex, Ir(ppy)3-based phosphorescent organic light-emitting devices (PHOLED). The devices were fabricated in the same run with a standard device without annealing for comparison, with an identical structure of indium tin oxide (ITO)/copper phthalocyanine (CuPc) (10 nm)/N,N′-di(naphthalene-l-yl)-N,N′-diphenyl-benzidine (NPB) (90 nm)/4,4′-bis(carbazol-9-yl)-biphenyl (CBP):Ir(ppy) (40 nm)/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) (15 nm)/tris(8-hydroxy-chinolinato) aluminum (Alq3) (40 nm)/Mg:Ag (200 nm)/Ag (20 nm). The annealing temperature used was 60, 80 and 100 °C, before deposition of BCP HBL or before Mg:Ag cathode, respectively. It was found that, before BCP deposition, 60 °C in situ post-growth annealing improves performance of the device, and the devices decay significantly with 80 and 100 °C annealing. The in situ post-growth annealed organic layers were characterized by photoluminescence and Raman spectroscopy.