1.53 μm electroluminescence from ErF3-doped organic light-emitting diodes

Near-infrared (NIR) organic light-emitting devices (OLEDs) are demonstrated by employing erbium fluoride (ErF3)-doped tris-(8-hydroxyquinoline) aluminum (Alq3) as the emitting layer. The device structure is ITO/N,N′-di-1-naphthyl-N,N′-diphenylbenzidine (NPB)/Alq3: ErF3/2,2′,2″-(1,3,5-phenylene)tris(1-phenyl-1H-benzimidazole) (TPBI)/Alq3/Al. Room-temperature electroluminescence around 1530 nm is observed due to the 4I13/2-4I15/2 transition of Er3+. Full width at half maximum (FWHM) of the electroluminescent (EL) spectrum is ∼50 nm. NIR EL intensity from the ErF3-based device is ∼4 times higher than that of Er(DBM)3Phen-based device at the same current. Alq3-ErF3 composite films are investigated by the measurements of X-ray diffraction (XRD), absorption, photoluminescence (PL) and PL decay time. Electron-only devices are also fabricated. The results indicate that energy transfer mechanism and charge trapping mechanism coexist in the NIR EL process.