Synthesis and photovoltaic performance of N-dioctylmethyl- 2,7-carbazole-alt-5,7-bis(thiophen-2-yl)-2,3-biphenylthieno3,4-b pyrazine copolymeric derivatives appending various donor units in phenyl moieties

摘要

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.