An organic thin-film transistor has a p-type semiconducting layer, wherein the semiconducting layer comprises a crystalline conjugated polyarylamine of the chemical structure: ##STR00001## wherein R.sub.1 through R.sub.5 are independently selected from hydrogen, alkyl having from about 1 to about 30 carbon atoms, aryl having from about 6 to about 40 carbon atoms, heteroaryl having from about 3 to about 40 atoms, alkoxy having from about 1 to about 30 carbon atoms, aryloxy having from about 6 to about 40 carbon atoms, and substituted derivatives thereof; wherein A and B are the same or different independently selected from arylenes having from about 6 to about 20 carbon atoms or heteroarylenes having from about 3 to about 20 carbon atoms; and wherein n is the degree of polymerization; and wherein the polyarylamine has a mobility (.mu..sub.0) of 10.sup.-4 cm.sup.2/Vsec or greater.