Electrospun Nanofibers of Blends of Conjugated Polymers:  Morphology, Optical Properties, and Field-Effect Transistors

Electrospun nanofibers of two series of binary blends of poly[2-methoxy-5-(2-ethylhexoxy)-1,4-phenylenevinylene] (MEH−PPV) with regioregular poly(3-hexylthiophene) (PHT) and with poly(9,9-dioctylfluorene) (PFO) were prepared, and their morphology and optical and electrical properties were characterized. Morphological and photophysical studies showed that the phase-separated domains in MEH−PPV/PHT nanofibers (30−50 nm) are much smaller as compared to blend thin films (100−150 nm), and efficient energy transfer was observed in these blend nanofibers. The MEH−PPV/PFO blend nanofibers had cocontinuous or core−shell structures, and significant energy transfer was absent in these blend nanofibers as compared to bulk thin films. Field-effect transistors based on MEH−PPV/PHT blend nanofibers showed exponential dependence of hole mobility on blend composition. The hole mobility decreased from 1 × 10 -4 cm 2 /(V s) in 20 wt % MEH−PPV blend nanofibers to 5 × 10 -6 cm 2 /(V s) at 70 wt %. If corrected for the reduced channel area of the transistors, the effective hole mobility varies from 5 × 10 -5 to 1 × 10 -3 cm 2 /(V s) and is similar to that of spin-coated blend thin films. Our results demonstrate that electrospun nanofibers of binary blends of conjugated polymers have tunable, composition-dependent, optical, and electronic properties that can be exploited in field-effect transistors.