Accelerated photopolymerization and increased mobility in C60 field-effect transistors studied by ultraviolet photoelectron spectroscopy

Ultraviolet photoelectron spectroscopy (UPS) of C60 thin-film field-effect transistors was measured with biasing gate voltages. A time-dependent change in the electronic structure of the C60 film was observed during the UPS measurement, which has never been observed in a C60 film grown on a conductive substrate. The change was attributed to the accelerated polymerization of C60 by comparing the UPS with that of the photopolymerized C60. The polymerization was associated with the increase in the field-effect electron mobility. This result indicates that mobile carriers produce reactive radicals in organic semiconductors.