Luminescence properties of poly(p-phenylenevinylene) derivatives carrying directly attached hole-transporting carbazole and electron-transporting phenyloxadiazole pendants

New poly(p-phenylenevinylene) (PPV) derivatives (polymer 1 and 2) that carry hole-transporting carbazole and electron-transporting phenyloxadiazole pendants were synthesized and their photo- and electroluminescence properties were studied. Polymer 1 is poly[2-(N-carbazolyl)-5-(2-ethylhexyloxy)-1,4- phenylenevinylene] that has both carbazole and 2-ethylhexyl pendant groups. And polymer 2 is poly[2-{4-[5-(4-i-butylphenyl)-l,3,4-oxadiazolyl]phenyl}-5-(2- ethylhexyloxy)-1,4-phenylenevinylene], which bears the 2-(4-t-butylphenyl)-5- phenyl-1,3,4-oxadiazole pendants. The optical properties of the polymer films were studied by UV-vis absorption, photoluminescence (PL) and electroluminescence (EL) spectroscopy. EL devices with the configuration of ITO/poly(3,4-ethylenedioxy-2,5-thienylene) (PEDOT) polymer/Ca/Al were constructed and the device performances were compared. Polymer 1 emits bright yellowish green light (max= 530 nm), whereas polymer 2 emits yellowish orange (λ_max= 540 nm) light. The device fabricated using polymer 1 showed a low turn-on electric field of 0.31 MV/cm and the maximum luminance of 30,390 cd/m² at 1.50 MV/cm. Polymer 2 exhibited a little poorer device performance (turn-on electric field: 0.94 MV/cm; maximum luminance: 5,720 cd/m² at 2.74 MV/cm Maximum photometric efficiencies of the devices were 4.4 and 1.3 cd/A, respectively.