Among all organic semiconductors, pentacene has been shown to have the highest thin film mobility reported to date. The crystalline structure of the first few pentacene layers deposited on a dielectric substrate is strongly dependent on the dielectric surface properties, directly affecting the charge mobility of pentacene thin film OTFTs. Herein, we report that there is a direct correlation between the crystalline structure of the initial submonolayer of a pentacene film and the mobility of the corresponding 60-nm-thick films showing terrace-like structure, as confirmed by 2D grazing-incidence X-ray diffraction and atomic force microscopy. Specifically, multilayered pentacene films, grown from single crystal-like faceted islands on HMDS-treated surface, have shown much higher charge mobility (mu = 3.4 +/- 0.5 cm2/Vs) than those with polycrystalline dendritic islands (mu = 0.5 +/- 0.15 cm2/Vs) on OTS-treated ones.

Flexible and conformable organic single crystals as thin as 150 nm are used for fabricating mechanically bendable organic single‐crystal field‐effect transistors on low‐cost plastic substrates (see figure and cover). We report effective field‐effect mobility as high as 4.6 cm2 V–1 s–1 for a flexible rubrene single‐crystal transistor, on/off ratio of ca. 106, threshold voltage of – 2.1 V, and a normalized subthreshold swing of 0.9 V nF decade–1 cm–2.