Polycondensation of thiophene-flanked cyanopyridine and carbazole via direct arylation polymerization for solar cell application

摘要

In this work, we report the synthesis of new pi-conjugated polymer designs through the polycondensation of 2-(octyloxy)-4,6-di(thiophen-2-yl)nicotinonitrile (M1) and 3,6-dibromo-9-octy1-9H-carbazole (2a) or 3,6-dibromo9-hexadecyl-9H-carbazole (2b) via palladium-catalysed direct arylation polymerization (DArP) reaction for solar cell application. The DArP reactions were carried out in three major solvents (i.e. toluene, dimethyformamide (DMF), and dimethylacetamide (DMA) with triphenylphosphine (as ligand), and K2CO3 (as base), respectively. Polymerization reaction conditions were carefully optimized with and without the addition of pivalic acid (PivOH) as additive. Interestingly, the polymer synthesized in PivOH and DMA solvent under the aforementioned reaction conditions yielded the considerably high molecular weight (M-n) of 21.1 kDa and PDI of 1.14 than the rest of polymeric reactions conditions. Thus, DArP reaction under Pd(OAc)(2), PPh3, K2CO3, PivOH and DMA conditions were found to be the ideal reaction conditions for the current monomeric systems. The synthesized polymer was used for photovoltaic studies and with the minimum optimization the obtained power conversion efficiency is reported.