Abstract
Oligothiophene derivatives DHB-4T, DFB-4T and pentacene derivatives DP-PT, DTh-PT, DTo-PT were synthesized and characterized as the active channel material in the organic FET. Structure of thin-film as a function of substrate surfaces ( bare silicon dioxide (SiO2/Si) substrate, n-octadecyltrichlorosilane (OTS/SiO2/Si)-, benzyltrichlorosilane (BTS/SiO2/Si)-, and 1,1,1,3,3,3-hexamethyldisilazane (HMDS/SiO2/Si)-treated surfaces) and temperature were examined. For DHB-4T, a near perpendicular molecular orientation was observed in most cases, with grain size increasing with increasing substrate temperature. Field effect mobilities were measured employing a top source-drain contact configuration. DHB-4T exhibited p-type semiconducting behavior with maximum field-effect mobility ranging from ~0.028 to ~0.17 cm2V-1s-1, depending on the substrate temperature. DP-PT and DTh-PT also exhibited p-type behavior with maximum field-effect mobilities ~ 10-3 cm2V-1s-1. Additionally, DHB-4T was also deposited on a rubbed SAM of n-nonyltrichlorosilane (NTS/SiO2/Si) and n-octadecyltricholrosilane (OTS/SiO2/Si) surfaces to examine the effect of rubbing on the crystal size and charge mobility.