Efficient organic electroluminescent devices based on an organosamarium complex

Several organic electroluminescent devices with different device structures were fabricated based on an organosamarium complex Sm(HFNH)3phen[HFNH=4, 4, 5, 5, 6, 6, 6-heptafluoro-1-(2-naphthyl)hexane-1, 3-dione; phen=1, 10-phenanthroline] as emitter. Their electroluminescent properties were investigated in detail. Although the devices with the optimal structure ITO/TPD (50 nm)/ Sm(HFNH)3phen (x wt%):CBP (50 nm)/BCP (20 nm)/AlQ (30 nm)/LiF (1 nm)/Al (200 nm) show high brightness (more than 400 cd/m2) and high current efficiency (about 1 cd/A), there are emissions from CBP, BCP and even from AlQ existing in the electroluminescence (EL) spectra besides emission from Sm(HFNH)3phen. The reason to this was discussed. The device with the structure ITO/TPD (50 nm)/Sm(HFNH)3phen (50 nm)/AlQ (30 nm)/LiF (1 nm)/Al (200 nm) exhibits the maximum brightness of 118 cd/m2 and current efficiency of 0.029 cd/A, and shows emissions from AlQ and Sm(HFNH)3phen at high voltages. However, with the BCP hole-block layer added, the device [ITO/TPD (50 nm)/Sm(HFNH)3phen (50 nm)/BCP (20 nm)/AlQ (30 nm)/LiF (1 nm)/Al (200 nm)] exhibits pure Sm3+ emission in the EL spectra even at high voltages, with the maximum current efficiency of 0.29 cd/A and brightness of 82 cd/m2.