[Spectral characteristics of novel small molecular fluorene derivative for organic light-emitting device]

Double-layer organic light-emitting devices (OLEDs) based on a blend system of novel small molecule fluorene material 6,6'-(9H-fluoren-9,9-diyl) bis(2,3-bis(9,9-dihexyl-9H-fluoren-2-yl) quinoxaline) (BFLBBFLYQ) and hole transporting material N, N'-biphenyl-N, N'-bis-(3-methylphenyl)-1, 1'-biphenyl-4, 4'-diamine (TPD) were fabricated. The structure of the double-layer device was ITO/BFLBBFLYQ : TPD/tris(8-hydroxyquinolinato) aluminum(Alq)/Mg : Ag. The photoluminescence (PL) spectra of BFLBBFLYQ and TPD were located at 447 and 414 nm, respectively. The spectral characteristics of the blend system and the double-layer device were investigated, which indicated that a new long wavelength emission peaking at 530 nm was appeared both in PL spectra and electroluminescence (EL) spectra. The exciplex between BFLBBFLYQ and TPD may play the role in long wavelength emission in the blend device and the spin-coated film. Based on the absorption spectra of a red fluorescent dye 4-(dicyanomethylene)-2-tert-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) as probe and the PL spectra of the blend system showing good overlap, energy transfer from the blend system to DCJTB could be expected. There fore, DCJTB could be selected as a molecular dopant to investigate the influence on EL spectra and the recombination of the devices. It was found that the excitons recombine at the interior Alq layer near to the BFLBBFLYQ : TPD layer.