Influence of gas molecules on the charge carrier mobility in thin films of semiconducting perylene tetracarboxylic imides

Thin films (30 nm) of crystalline N,N'-dimethylperylene-3,4,9,10-biscarboximide (MePTCDI) or amorphous 1,6,7,12-tetrachloro-N,N'-dimethylperylene-3,4,9,10-biscarboximide (Cl4MePTCDI) were prepared by physical vapor deposition and characterized by conductivity and field effect measurements at pristine films and under increasing partial pressure of oxygen, ethanol, acetone, or n-butane. Changes in the conductivity of the films were observed. Field effect measurements served to differentiate between changes in the charge carrier mobility mu and changes of the charge carrier concentration n. mu was found to decrease significantly, whereas rather small changes were found in n. Gas molecules that diffused into the films changed mu at least ten times more efficiently than those molecules just adsorbed on the surface. (c) 2006 American Institute of Physics.