HIGHLY MOBILE ELECTRONS AND HOLES ON ISOLATED CHAINS OF THE SEMICONDUCTING POLYMER POLY(PHENYLENEVINYLENE)

The nature of the charge carriers in 'conducting' polymers is of consi derable interest at present(1,2), largely on the basis of the technolo gical potential of these materials for use as the semiconducting layer in field-effect transistors (FETs) and the emissive layer in light-em itting diodes(3) (LEDs). One of the main outstanding questions concern s the relative importance of intra- versus inter-chain charge transfer in determining the overall rate of charge transport. Here we apply th e pulse-radiolysis time-resolved microwave conductivity technique(4) t o dilute solutions of a soluble dialkoxy derivative of the semiconduct ing polymer poIy(phenylene vinylene), PPV, by which means we determine the one-dimensional intra-chain mobilities of electrons and holes on isolated polymer chains free from inter-chain interactions. The values so obtained-0.5 and 0.2 cm(2)V(-1)s(-1) respectively-are considerably larger than the mobilities measured previously for bulk PPV-based mat erials(5-9). This suggests that considerable improvement in the perfor mance characteristics (in particular switching time and maximum curren t) of organic FET and LED devices should be possible if material purit y and structural order can be better controlled.