title: Fabrication and characterization of organic light-emitting diodes using zinc complexes as hole-blocking layer.
abstract: 2-(2-Hydroxyphenyl)benzoxazole (HPB) was employed as organic ligand and the corresponding zinc complexes (Zn(HPB)2 and Zn(HPB)q) were synthesized. And their EL properties were characterized. The structures of zinc complexes were determined with FT-NMR, FT-IR, UV-Vis, and XPS. The thermal stability showed up to about 300 degrees C under nitrogen flow, which was measured by TGA. The photoluminescence (PL) of zinc complexes were measured from the DMF solution. The PL emitted in blue and yellow region, respectively. The EL devices were fabricated by the vacuum deposition. Two kinds of OLEDs devices were fabricated; ITO/NPB (40 nm)/Zn complexes (60 nm)/LiF/Al and ITO/NPB (40 nm)/Alq3 (60 nm)/Zn complexes (5 nm)/LiF/Al. Both of the EL properties as the emitting and the hole-blocking layer were investigated. The EL emission of Zn(HPB)q exhibited green light centered at 532 nm. The device showed a turn-on voltage at 5 V and a luminance of 6073 cd/m2 at 10 V. Meanwhile, the maximum EL the emission of the Zn(HPB)2 device was found to be at 447 nm. And the device showed a luminance of 2813 cd/m2 at 10 V. The ITO/NPB (40 nm)/Alq3 (60 nm)/Zn(HPB)2 (5 nm)/LiF/Al device showed increased luminance of L=17000 cd/m2 compared to L=12000 cd/m2 for similar device fabricated without the hole-blocking layer. And the turn-on voltage was significantly affected by the existence of the hole-blocking layer.
authors.affiliation: Department of Chemistry and BPRC, Inje University, Gimhae 621-749, Korea.
authors.forename: Won Sam
authors.initials: WS
authors.lastname: Kim
authors.forename: Jung Min
authors.initials: JM
authors.lastname: You
authors.forename: Burm-Jong
authors.initials: BJ
authors.lastname: Lee
authors.forename: Yoon-Ki
authors.initials: YK
authors.lastname: Jang
authors.forename: Dong-Eun
authors.initials: DE
authors.lastname: Kim
authors.forename: Young-Soo
authors.initials: YS
authors.lastname: Kwon
mesh_terms: D000535:Aluminum / Q000737:chemistry; D001583:Benzoxazoles / Q000737:chemistry*; D004563:Electrochemistry / Q000379:methods*; D008024:Ligands; D008027:Light; D008956:Models, Chemical; D036103:Nanotechnology / Q000295:instrumentation / Q000379:methods*; D009584:Nitrogen / Q000737:chemistry; D010777:Photochemistry / Q000379:methods; D013053:Spectrophotometry / Q000379:methods; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D014466:Ultraviolet Rays; D015032:Zinc / Q000737:chemistry*; D017967:Zinc Compounds / Q000737:chemistry
chemical_list: D001583:Benzoxazoles; D008024:Ligands; D017967:Zinc Compounds; D000535:Aluminum; D015032:Zinc; D009584:Nitrogen