Synthesis and electroluminescence properties of carbazole-containing 2,6-naphthalene-based conjugated polymers

Three types of carbazole containing 1,5-disubstituted poly(2,6-naphthalene) derivatives, i.e., 2,6-naphthalene homopolymer that has a carbazolyl side chain at 1,5-positions, random copolymers and alternating copolymers consisting of 1,5-dialkoxynaphthalene-2,6-diyl and N-phenylcarbazole-2,7-diyl were newly synthesized by Ni-mediated Yamamoto polycondensation and Pd-catalyzed Suzuki coupling reaction. The number-average molecular weights (Mn) of the polymers and their polydispersity indices (Mw/Mn) were 5.4–8.2 × 103 and 1.4–1.7, respectively. These polymers exhibited blue photoluminescence in the film states and high fluorescence quantum efficiencies in CHCl3 (ϕfl = 0.70–1.00). The electroluminescence properties of these polymers were investigated by fabricating a PLED device that has a configuration of ITO/PEDOT(PSS)/polymer/CsF/Al. The device fabricated with the random copolymer exhibited highest performances showing a maximum brightness of 8370 cd/m2 at 13 V and a maximum efficiency of 2.16 cd/A at 7 V.