2, Dongguk University, Seoul, , Korea (the Republic of)
We report synthesis of two highly planar conjugated polymers based on planar 4,7-bis(4,4-bis(2-ethylhexyl)-4H-silolo[3,2-b:4,5-b']dithiophen-2-yl)-5,6-difluorobenzo[c][1,2,5]thiadiazole (DFD) moieties: PDFDT and PDFDSe that are structured by a repeating unit of DFD-thiophene or DFD-seleonophene, respectively. Comparative study revealed that PDFDSe polymer tends more aggregating in solution phase and generates a more oxidizable conjugated system and better packed crystalline states in films with exclusive edge-on orientations. PDFDSe-based organic thin film transistor (OTFT) with Top gate bottom contact geometry performed better than PDFDT-based OTFT. With poly(methyl methacrylate) (PMMA) gate dielectric layer, the PDFDSe OTFT achieved a reasonably high hole mobility µ = 2.72 cm2V-1s-1 with high reproducibility. This value increases remarkably to μ = 8.52 and 20.3 cm2V-1s-1, respectively, for a high k-polymeric dielectric of poly(vinylidenefluoride-trifluoroethylene) (P(VDF-TrFE)) and a solid-state electrolyte gate insulator (SEGI) composed of P(VDF-TrFE)/poly(vinylidene fluoride-co-hexafluroropropylene)/1-ethyl-3-methylimidazolium bis(trifluoro-methylsulfonyl)imide. This improvement was attributed to the high carrier density in the semiconducting channel region, induced by the high dielectric layer capacitance. The achievement of this excellent carrier mobility demonstrates a great potential of conjugated polymers as electronic components in future electronic applications.