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Two new bithiophene imide (BTI)-based n-type polymers were synthesized. f-BTI2-FT based on a fused BTI dimer showed a smaller band gap, a lower LUMO, and higher crystallinity than s-BTI2-FT containing a BTI dimer connected through a single bond. s-BTI2-FT exhibited a remarkable electron mobility of 0.82 cm2 V−1 s−1, and f-BTI2-FT showed a further improved mobility of 1.13 cm2 V−1 s−1 in transistors. When blended with the polymer donor PTB7-Th, f-BTI2-FT-based all-polymer solar cells (all-PSCs) attained a PCE of 6.85 %, the highest value for an all-PSC not based on naphthalene (or perylene) diimide polymer acceptors. However, s-BTI2-FT all-PSCs showed nearly no photovoltaic effect. The results demonstrate that f-BTI2-FT is one of most promising n-type polymers and that ring fusion offers an effective approach for designing polymers with improved electrical properties. [ABSTRACT FROM AUTHOR]

Abstract: Multicharged ions (, , , ) at constant speed (Bohr velocity) were used to irradiate PC (polycarbonate) foils which were subsequently chemically etched. Because of the low ion dose of , pores on the surface were discrete. The diameters of the pores were measured by means of scanning electron microscopy (SEM). From the linear dependence of the pore diameter on the etching time, the transversal etching rate can be obtained. It was found that the transversal etching rate decreased with ion charge. These results can mainly be explained by the variation of the charge exchange process for ions with a different charge state. [Copyright &y& Elsevier]

Abstract: The size of alpha-particle tracks on electrochemically etched ultraviolet-irradiated polyallyldiglycol carbonate (PADC) films were studied. PADC films were first irradiated with 3MeV alpha particles and then pre-etched chemically using aqueous 6.25N NaOH solution for 2h. The films were then exposed to incoherent broad-band ultraviolet (UV) radiation provided by a mercury lamp for different durations up to 2h. The films were then electrochemically etched in a 6.25N NaOH solution, with an a.c. voltage of about 1200 and a frequency of 5kHz, for 2h at room temperature. The mean sizes of the tracks (or trees) were measured and were found to increase for short UV exposures and decrease for prolonged UV exposures. The results can be explained by the dominance of chain scission at the beginning of UV exposure and the dominance of cross linking for prolonged UV exposure. This explanation is further supported by results from X-ray photo-electron spectroscopy (XPS). Here, the C–O–C bonds decrease for short UV exposures, which is explained by scission of the polymer chains, and increase again for prolonged UV exposure, which indicates cross linking. From nano-indentation measurements, the hardness and the reduced modulus increase monotonically with the UV irradiation. Apparently, these quantities only characterize the amount of cross linking, and do not give information on the initial scission process. [Copyright &y& Elsevier]