DRIFT MOBILITY OF HOLES IN VACUUM-DEPOSITED FILMS OF ZINC TETRAPHENYLPORPHYRIN

Drift mobilities (mu) of holes in zinc tetraphenylporphyrin (ZnTPP) fi lms were measured using the time-of-flight method. The plot of log mu vs. a square root of electric field (E(1/2)) fit a straight line and i ts extrapolation to E=O yielded an extremely small mu value of the ord er 10(-10) cm(2) V-1 s(-1) at 20 degrees C. The field dependencies of the hole mobilities at different temperatures were analyzed on the bas is of the disorder formalism developed by Bassler and co-workers. As a result, the slow hole transport in the ZnTPP films was ascribed to a greater energetic disorder parameter(sigma=0.15 eV) resulting from a n early amorphous structure of the ZnTPP films.