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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 28, Number 12
BKCSDE 28(12)
December 20, 2007 

 
Title
Synthesis and Properties of PCPP-Based Conjugated Polymers Containing Pendant Carbazole Units for LEDs
Author
Youngeup Jin, Sun Hee Kim, Hyojin Lee, Suhee Song, Yunna Kim, Han Young Woo, Kwanghee Lee, Hongsuk Suh*
Keywords
Light emitting diode, PCPP, Carbazole
Abstract
New poly(cyclopenta[def]phenanthrene) (PCPP)-based conjugated copolymers, containing carbazole units as pendants, were prepared as the electroluminescent (EL) layer in light-emitting diodes (LEDs) to show that most of them have higher maximum brightness and EL efficiency. The prepared polymers, Poly(2,6-(4-(6-(Ncarbazolyl)- hexyl)-4-octyl-4H-cyclopenta[def]phenanthrene)) (CzPCPP10) and Poly(2,6-(4-(6-(N-carbazolyl)- hexyl)-4-octyl-4H-cyclopenta[def]phenanthrene))-co-(2,6-(4,4-dioctyl-4H-cyclopenta[def]phenanthrene)) (CzPCPP7 and CzPCPP5), were soluble in common organic solvents and used as the EL layer in light-emitting diodes (LEDs) of configuration with ITO/PEDOT/polymer/Ca/Al device. The polymers are thermally stable with glass transition temperature (Tg) at 77-100 °C and decomposition temperature (Td) at 423-457 °C. The studies of cyclic voltammetry indicated same HOME levels in all polymers, although the ratios of carbazole units are different. In case of PLEDs with configuration of ITO/PEDOT/CzPCPPs/Ca/Al device, The EL maximum peaks were around 450 nm, which the turn-on voltages were about 6.0-6.5 V. The maximum luminescence of PLEDs using CzPCPP10 was over 4400 cd/m2 at 6.5 V, which all of the maximum EL efficiency were 0.12 cd/A. The CIE coordinates of the EL spectrum of PLEDs using CzPCPP10 was (0.18, 0.08), which are quite close to that of the standard blue (0.14, 0.08) of NTSC.
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