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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 29, Number 1
BKCSDE 29(1)
January 20, 2008 

Poly(p-phenylenevinylene)s Derivatives Containing a New Electron-Withdrawing
CF3F4Phenyl Group for LEDs
Youngeup Jin, Jeung Hee Kang, Suhee Song, Sung Heum Park, Jihyun Moon, Han Young Woo, Kwanghee Lee, Hongsuk Suh*
Electroluminescence, PPV, Electron-withdrawing group, Polymer light emitting diodes (PLEDs)
New PPV derivatives which contain electron-withdrawing CF3F4phenyl group, poly[2-(2-ethylhexyloxy)-5- (2,3,5,6-tetrafluoro-4-trifluoromethylphenyl)-1,4-phenylenevinylene] (CF3F4P-PPV), and poly[2-(4-(2-etylhexyloxy)- phenyl)-5-(2,3,5,6-tetrafluoro-4-trifluoromethylphenyl)-1,4-phenylenevinylene] (P-CF3F4P-PPV), have been synthesized by GILCH polymerization. As the result of the introduction of the electron-withdrawing CF3F4phenyl group to the phenyl backbone, the LUMO and HOMO energy levels of CF3F4P-PPV (3.14, 5.50 eV) and P-CF3F4P-PPV (3.07, 5.60 eV) were reduced. The PL emission spectra in solid thin film are more redshifted over 50 nm and increased fwhm (full width at half maximum) than solution conditions by raising aggregation among polymer backbone due to electron withdrawing effect of 2,3,5,6-tetrafluoro-4- trifluoromethylphenyl group. The EL emission maxima of CF3F4P-PPV and P-CF3F4P-PPV appear at around 530-543 nm. The current density-voltage-luminescence (J-V-L) characteristics of ITO/PEDOT/polymer/Al devices of CF3F4P-PPV and P-CF3F4P-PPV show that turn-on voltages are around 12.5 and 7.0 V, and the maximum brightness are about 82 and 598 cd/m2, respectively. The maximum EL efficiency of P-CF3F4P-PPV (0.51 cd/A) was higher than that of CF3F4P-PPV (0.025 cd/A).
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