Efficient Electron Mobility in an All-Acceptor Napthalenediimide-Bithiazole Polymer Semiconductor with Large Backbone Torsion

An all-acceptor napthalenediimide-bithiazole-based copolymer, P(NDI2OD-BiTz), was synthesized and characterized for application in thin-film transistors. Density functional theory calculations point to an optimal perpendicular dihedral angle of 90 degrees between acceptor units along isolated polymer chains; yet optimized transistors yield electron mobility of 0.11 cm(2)/(V s) with the use of a zwitterionic naphthalene diimide interlayer. Grazing incidence X-ray diffraction measurements of annealed films reveal that P(NDI2OD-BiTz) adopts a highly ordered edge-on orientation, exactly opposite to similar bithiophene analogs. This report highlights an NDI and thiazole all acceptor polymer and demonstrates high electron mobility despite its nonplanar backbone conformation.