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Carolyn Buckley1 Zhibo Yuan1 Guoyan Zhang1 Elsa Reichmanis1

1, Georgia Institute of Technology, Atlanta, Georgia, United States

The development of semiconducting conjugated polymers for organic thin film transistors (OTFTs) has been the focus of intense research efforts for their key role in plastic electronics, as well as a vision of solution processability leading to reduced costs in device fabrication relative to their inorganic counterparts. The pursuit of high-performance n-channel (electron transporting) polymer semiconductors vital to the development of robust and low-cost organic integrated circuits has faced significant challenges; mainly for poor ambient operational stability and OTFT device performance lagging far behind that of p-channel organic semiconductors (OSCs). As an alternative to the ubiquitous donor-acceptor (DA) molecular design strategy, we have fabricated a novel conjugated n-channel polymer using an all-acceptor (AA) unipolar approach. Previously, we have synthesized a high performance AA polymer, PDPP4Tz, in which bithiazole building blocks were incorporated to lower the HOMO and LUMO energy levels. PDPP4Tz showed all electron transporting mobility as high as 0.07 cm2V-1s-1. In order to further understand the impact of electron withdrawing moieties to conjugated polymer device performance, we have synthesized a new conjugated polymer, poly(2-(2-decyltetradecyl)-6-(5-(5’-methyl-[2,2’-bithiaol]-5-yl)-3-(5-methylpyridin-2-yl)-5-(tricosan-11-yl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione) (DPPDPy-BTz). As an analog to benzene, the pyridine in DPPDPy-BTz is proven to lower the energy levels to achieve n-channel performance. By incorporating another electron deficient bithiazole building blocks, the preliminary electron FET mobility of the polymer is shown to be 5x10-4 cm2V-1s-1. In comparison with the known DPPDPyBT, it is shown that by substituting bithiophenes with bithiazoles, we successfully lower the HOMO/LUMO energy of the DPPDPyBTz to make another all-electron transporting polymer.

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