A series of N-dioctylmethyl-2,7-carbazole-alt-5,7-bis(thiophen-2-yl)-2,3-biphenylthieno[3,4-b]pyrazine(PCz-3Th Pz-Ph)copolymeric derivatives appending various donor units in two phenyl rings,namely,PCz-3Th Pz-Ph Th,PCz-3Th Pz-Ph Fl,PCz-3Th Pz-Ph Cz,and PCz-3Th Pz-Ph Tpa were synthesized and characterized.The effect of these appending donor units,e.g.,thiophene(Th),fluorene(Fl),carbazole(Cz),and triarylamine(Tpa),was investigated on dispersible,optical,electrochemical,and photovoltaic properties for their polymers.The copolymers of PCz-3Th Pz-Ph Cz and PCz-3Th Pz-Ph Tpa containing Cz or Tpa units exhibited higher short-circuit current density(Jsc)and power conversion efficiency(PCE)in their bulk heterojunction polymeric solar cells.The highest PCE of 1.66%and Jsc of 7.16 m A cm 2 were obtained in a device with the PCz-3Th Pz-Ph Cz/PC61BM blend under AM 1.5 G irradiation(100 m W cm 2);these values are 1.78 and 1.59 times higher than the corresponding values for the PCz-3Th Pz-Ph-based device.When PC61BM was placed by PC71BM,the PCz-3Th Pz-Ph Cz-based device displayed an enhanced PCE of 2.98%and a Jsc of 10.88 m A cm 2.This work demonstrated that appending additional hole-transporting units of Cz and Tpa into the side-chain of a polymer with a D-A backbone can significantly enhance the photovoltaic performance of their resultant polymers.
Polymer light-emitting diodes(PLEDs) containing Eu(DBM)3(Br DPPz)(DBM is dibenzoylmethane, and Br DPPz is 11- bromo-dipyrido[3,2-a:2′,3′-c]phenazine) doped in a blend of poly(9,9-dioctylfluorene)(PFO) and 2-tert-butylphenyl-5- biphenyl-1,3,4-oxadiazole(PBD) as the host matrix were reported. Eu(DBM)3(Br DPPz) exhibited high thermal stability and intense UV-Vis absorption. Narrow-bandwidth red emission at 612 nm with a full width at half-maximum(FWHM) of 14.0 nm was observed from Eu(DBM)3(Br DPPz) in these double-layered PLEDs at dopant concentrations from 1 wt% to 8 wt%. For the PLED containing 1 wt% Eu(DBM)3(Br DPPz), a maximum luminance of 829 cd/m2 at 153.5 m A/cm2, highest external quantum efficiency of 1.70% at 2.1 m A/cm2 and maximum luminance of 0.74 cd/A at 4.31 m A/cm2 were obtained.
Qunping FanYu LiuZhaoran HaoChun LiYafei WangHua TanWeiguo ZhuYong Cao
