Precisely Controlling the Structure of Ultrathin Semiconducting Films by a Laminating Method for High-Performance Organic Field-Effect Transistors.

High-performance organic field-effect transistors (OFETs) based on conjugated polymers have received extensive attention in recent years. However, the relationships between the multiscale structures of conjugated polymers and electrical properties are not well established. Here, laminated, ultrathin poly(3-hexylthiophene) (P3HT) films have been prepared using a sequential, repeated transfer-etching process from the precursor conjugated/insulating polymer blend films and used to study the structure-property relationship at the transition of the film structure from 2D to 3D. The molecular packing of the films is improved by lamination as certified by grazing incidence X-ray diffraction, UV-visible spectroscopy, and Raman spectroscopy. The laminated ultrathin P3HT films exhibit excellent electrical properties with a maximum mobility of 0.23 cm2 V-1 s-1 at three layers, which is close to the highest value reported for undoped P3HT OFETs. Temperature-dependent FET characteristics reveal that the laminated films have low activation energy and a 2D charge transport profile regardless of the number of layers. These charge transport properties are attributed to the well-ordered molecular packing and low trap density in the films, which are enabled by the phase separation of the precursor blend films and the lamination process. In addition, OFETs based on these films have good photostability under different wavelengths of light, indicating that this approach has promising practical application prospects.