SEMICONDUCTOR PROPERTIES OF SOLUTION-DOPED POLYPHENYLACETYLENE

The authors report some of the properties of what they believe to be homogeneously doped PPA-I//2 and PPA-AsF//5. The latter shows promising semiconductor properties. It is also stable in the atmosphere, in contrast to AsF//5-doped polyacetylene (PA) or other conjugated polymers doped with AsF//5 in gas-solid reaction. Results show that iodine cannot be removed from PPA-I//2 by pumping from solution-doped PPA, except that in part at y greater than 0. 4. PPA-I//2 shows very substantial ionic conductivity upon its formation in chloroform solution, but the conductivity drops by many orders of magnitude as the films dry. The satisfactory reproducibility of the results on exhaustively dried films suggests uniform doping. By contrast, the authors have been unable to obtain reproducible resistivities with PPA-I//2 doped in a solid-vapor reaction. Nonetheless, Schottky barrier diodes which exhibit a photovoltaic effect can be formed from vapor-doped, as well as solution-doped, PPA-I//2.