High performance p-channel transistors based on a single-crystal organic microribbon self-assembled through a solution process, are achieved by enhancing the crystallinity, improving the interface between the dielectric and the crystal, shrinking the channel length, and realizing asymmetric metal electrodes for source and drain (see figure). The highest mobility reached is 2.1 cm(2)V(-1)s(-1) with an on/off ratio of 2 x 10(5) and a threshold voltage of -7V.