The use of single crystals has been fundamental to the development of semiconductor microelectronics and solid-state science1. Whether based on inorganic2, 3, 4, 5 or organic6, 7, 8 materials, the devices that show the highest performance rely on single-crystal interfaces, with their nearly perfect translational symmetry and exceptionally high chemical purity. Attention has recently been focused on developing simple ways of producing electronic devices by means of printing technologies. ‘Printed electronics’ is being explored for the manufacture of large-area and flexible electronic devices by the patterned application of functional inks containing soluble or dispersed semiconducting materials9, 10, 11. However, because of the strong self-organizing tendency of the deposited materials12, 13, the production of semiconducting thin films of high crystallinity (indispensable for realizing high carrier mobility) may be incompatible with conventional printing processes. Here we develop a method that combines the technique of antisolvent crystallization14 with inkjet printing to produce organic semiconducting thin films of high crystallinity. Specifically, we show that mixing fine droplets of an antisolvent and a solution of an active semiconducting component within a confined area on an amorphous substrate can trigger the controlled formation of exceptionally uniform single-crystal or polycrystalline thin films that grow at the liquid–air interfaces. Using this approach, we have printed single crystals of the organic semiconductor 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) (ref. 15), yielding thin-film transistors with average carrier mobilities as high as 16.4 cm2 V−1 s−1. This printing technique constitutes a major step towards the use of high-performance single-crystal semiconductor devices for large-area and flexible electronics applications.
Figures at a glance
Figure 1: Inkjet printing of organic single-crystal thin films. 
a, Schematic of the process. Antisolvent ink (A) is first inkjet-printed (step 1), and then solution ink (B) is overprinted sequentially to form intermixed droplets confined to a predefined area (step 2). Semiconducting thin films grow at liquid–air interfaces of the droplet (step 3), before the solvent fully evaporates (step 4). b, Micrographs of a 20 × 7 array of inkjet-printed C8-BTBT single-crystal thin-films. c, Crossed Nicols polarized micrographs of the film. d, Expanded micrograph of the film, showing stripes caused by molecular-layer steps. e, Atomic-force microscopy image and the height profile (below) showing the step-and-terrace structure on the film surfaces.
Figure 2: Synchrotron-radiated single-crystal X-ray diffraction and polarized absorption spectra. 
Oscillation photographs for out-of-plane diffraction (a) and for high-incident-angle diffraction (b) of inkjet-printed C8-BTBT single-crystal thin films, where ω is the incident angle. The Bragg reflections observed in b correspond to the indices, which contain in-plane components. The refined unit cell obtained from the reflections is consistent with that of the bulk crystal. c, Polarized optical absorption spectra with coefficient α and with polarization parallel to the a and b axes in the single-crystal film, demonstrating optical anisotropy with regard to these principal axes. d, View of the molecular arrangement of C8-BTBT in the crystal21.
Figure 3: Transistor characteristics for the inkjet-printed C8-BTBT single-crystal thin films. 
a, Schematic of the device structure and micrograph of the thin-film transistors. b, Distribution of mobility and on/off ratio measured over 54 transistors. Average mobility is 16.4 ± 6.1 cm2 V−1 s−1. c, Transfer characteristics at Vsd = −60 V. d, Output characteristics at various gate voltages Vg.
