Nitrogen-embedded small-molecule semiconducting materials: Effect of chlorine atoms on their electrochemical, self-assembly, and carrier transport properties

摘要： We reported three novel nitrogen-embedded small molecules 4a, 4b, and 4c, which were synthesized from the condensation reactions of benzo[1,2-b:4,5-b']difuran-2,6(3H,7H)-dione with 1-(2-ethylhexyl)-1H-pyrrolo[2,3-b]pyridine-2,3-dione, 6-chloro-1-(2-ethylhexyl)-1H-pyrrolo[2,3-b]pyridine-2,3-dione, or 4,6-dichloro-1-(2-ethylhexyl)-1H-pyrrolo[2,3-b]pyridine-2,3-dione, respectively. Their optical, electrochemical properties, self-assembly behavior, and carrier transport properties were studied by a range of experimental and theoretical methods, and the effect of chlorine atoms were well discussed. Energy levels of the highest occupied molecular orbitals and the lowest unoccupied ones for these molecular materials locate at ?5.92～?6.02 and ?4.25～?4.37 eV, respectively. Bottom gate/bottom contact field-effect transistors based on 4a, 4b, and 4c exhibited n-channel transport characteristics with the highest electron mobility of 7.57 × 10?3 cm2 V?1 s?1. Thin film microstructure investigations revealed 4a and 4c perform lamellar molecular packing with random orientations to the OTS-treated SiO2 substrate, while 4b conducts a highly crystalline, edge-on, lamellar packing though large grain boundaries exist in its thin film.