We develop two donoracceptor copolymers based on a fluorinated dithienylethene building block, namely PNFDTE1 and PNFDTE2, in which naphthalenediimide (NDI) acts as an acceptor unit. Thermogravimetric analysis displayed both copolymers having good thermal stability with high decomposition temperatures over 400 degrees C. Broad absorption spectra were observed in the UVvisNIR region, with the absorption maxima being 720 and 724 nm for PNFDTE1 and PNFDTE2, respectively. Cyclic voltammetry tests exhibited deep-lying lowest unoccupied molecular orbital energy levels of ca. -4.0 eV. Two-dimensional grazing incidence X-ray diffraction patterns showed that different packing modes for two polymers result in the variation in charge transport properties. Backbone fluorination effectively decreases electron injection barrier, thereby facilitating electron mobility. An impressive electron mobility of 3.20 cm V-1 s(-1) was achieved in air for PNFDTE1-based polymer field-effect transistors fabricated on the poly(ethylene terephthalate) substrate. The mobility value is almost the highest for NDI-containing polymers on the flexible substrate. This work provides a guideline for design and synthesis of fluorinated semiconductors that enables control of charge-transport polarity.