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Narrow band gap benzodithiophene and quinoxaline bearing conjugated polymers for organic photovoltaic applications

2020-09-01
Caliskan, Meric
Erer, Mert Can
Aslan, Sultan Taskaya
Udum, Yasemin Arslan
Toppare, Levent Kamil
Çırpan, Ali
The reasonable selection and optimization of donor-acceptor units allow the band gap tuning as well as the light absorption ability and the energy levels of the photoactive layer of Bulk Heterojunction (BHJ) solar cells. In this work, a series of new quinoxaline and selenophene based benzo[1,2-b:4,5-b'] dithiophene (BDT) bearing conjugated polymers were synthesized via Pd (0) catalyzed Stille polycondensation reaction. The 2-(2-octyldodecyl) selenophene ring was attached to 4th and 8th positions of phenyl ring in BDT to obtain donor moiety and three different quinoxaline moieties as acceptors were introduced into the BDT backbone. After completion of synthesis of desired polymers, their structures were identified with H-1 NMR spectroscopy and their number and weight average molecular weights were examined with gel permeation chromatography (GPC). The effects of introducing fused structure and incorporation of an electron withdrawing F atom to the quinoxaline part on the electrochemical, spectroelectmchemical, optical and morphological properties of the synthesized polymers were examined and correlated to the photovoltaic performance. Both polymers namely P1, P2 and P3 were utilized as donor segments in active layer. They were combined with PC71 BM ([6,6]-phenyl C-71-butyric acid methyl ester) as the acceptor to fabricate bulk heterojunction solar cells. Highest power conversion efficiencies were found as 2.36% for P1, 2.07% for P2 and 2.45% for P3 under AM 1.5 G (100 mW/cm(2)) conditions.