Improver efficiencies of light-emitting diodes through incorporation of charge transporting components in tri-block polymers

摘要

9,9-Di-n-hexylfluorene-co-anthracene (DHF-ANF)random copolymer and triphenylamine (TPA)- and oxadiazole(OXA)- containing tri-block copolymers along with a crosslinkedTPA polymer are used to fabricate single- and double-layer lightemitting diodes (LEDs). In both single-layer and double-layerdevices, TPA hole transporting components improve hole injectionand transport, leading to improved device performance when lowwork function calcium (Ca) is used as the cathode, whereas OXAelectron transporting components improve electron injection whenhigh work function aluminum (Al) is used. This suggests thatDHF-ANT copolymer and DHF-ANT blocks in the two tri-blockpolymers are hole-limited in devices with Ca cathodes, andelectron-limited with Al cathodes. Furthermore, double-layerdevices including a separate hole transporting crosslinked TPAlayer increase device efficiencies by at least one order in magnitudeover the corresponding single-layer devices, due to the improvedcharge injection, charge confinement and charge recombination.999Elsevier science S.A. All rights reserved.