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Synthesis and Luminescent Properties of Blue Light Emitting Polymers Containing both Hole and Electron Transporting Units
Author(s) -
Ahn Taek,
Shim HongKu
Publication year - 2001
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/1521-3935(20011101)202:16<3180::aid-macp3180>3.0.co;2-v
Subject(s) - materials science , electroluminescence , carbazole , photoluminescence , fluorene , polymer , thermal stability , polymer chemistry , photochemistry , indium tin oxide , luminescence , phenylene , light emitting diode , chemistry , organic chemistry , optoelectronics , thin film , nanotechnology , layer (electronics) , composite material
Poly[(oxy‐4,4′‐octafluorobiphenyloxy)‐1,4‐phenylenevinylene‐2‐methoxy‐5‐(2‐ethylhexyloxy)‐1,4‐phenylenevinylene‐1,4‐phenylene], POFB‐MEH‐PPV, poly[(oxy‐4,4′‐octafluorobiphenyloxy)‐1,4‐phenylenevinylene‐9,9‐dihexyl‐2,7‐fluorenediylvinylene‐1,4‐phenylene], POFB‐PF, and poly[(oxy‐4,4′‐octafluorobiphenyloxy)‐1,4‐phenylenevinylene‐ N ‐ethylhexyl‐3,6‐carbazolevinylene‐1,4‐phenylene], POFB‐PK, were synthesized by the well‐known Wittig condensation polymerization. We incorporated the high electron affinity (octafluorobiphenyl) and hole‐transporting (carbazole, fluorene, and dialkoxyphenyl) units into the conjugated main chain. The conjugation lengths are limited to the blue‐emission region by ether linkage. The resulting polymers were completely soluble in common organic solvents such as chloroform, 1,2‐dichloroethane, and cyclohexanone, and exhibited good thermal stability up to 300°C. The synthesized polymers showed UV‐visible absorbance and photoluminescence (PL) in the ranges of 350–385 nm and 460–490 nm, respectively. The fluorene or carbazole containing POFB‐PF and POFB‐PK showed blue photoluminescence peaks at 470 and 460 nm, respectively. The single‐layer light‐emitting diode was fabricated in a configuration of ITO (indium‐tin oxide)/polymer/Al. Electroluminescence (EL) emission of POFB‐PF and POFB‐PK were shown at 475 and 458 nm, respectively, corresponding to the pure blue emissions. And, a dialkoxyphenyl containing POFB‐MEH‐PPV showed greenish blue light at 494 nm. But, LED devices from synthesized polymers showed poor device performance and high turn on voltage. So, we fabricated light‐emitting diodes (LEDs) from blend polymers composed of poly[2‐methoxy‐5‐(2‐ethylhexyloxy)‐1,4‐phenylenevinylene] (MEH‐PPV) and POFB‐MEH‐PPV (POFB‐PF or POFB‐PK) as the emitting layers. The EL emission maxima of each blend polymers were in the range of 573–591 nm, which indicates that the emission is mainly due to MEH‐PPV and POFB‐MEH‐PPV (POFB‐PF or POFB‐PK) contributes to the enhancement of the luminescence. And each blend polymers exhibited higher EL quantum efficiency compared with MEH‐PPV at the same current density.