Role of processing solvents in photocarrier transport of polyanilines

Transient photoconductivity measurements have been performed on polyaniline (PAN), poly(2-methoxyaniline) (PMA) and poly(2-fluoroaniline) (PFA) films by means of the time-of-flight technique. The effect of processing solvents such as N-methylpyrrolidinone (NMP) and dichloromethane on the nature of transient photocurrent signals is discussed. In the NMP-cast PAN, PFA and PMA films, the photocurrent was composed of only short-lived components, which did not show the sign of transit time. On the other hand, the PMA film cast from dichloromethane showed a long-lived component of photocurrent with the presence of a field-dependent kink due to the transit time. PAN and PFA are least soluble in dichloromethane. The room-temperature hole mobility of PMA cast from dichloromethane solution has been found to be 1.2 × 10-5 cm2/V&middots at an applied field of 1.0 × 106 V/cm.