Solution processibility is a unique advantage of organic semiconductors, permitting the low-cost production of flexible electronics under ambient conditions. However, the solution affinity to substrate surfaces remains a serious dilemma; liquid manipulation is more difficult on highly hydrophobic surfaces, but the use of such surfaces is indispensable for improving device characteristics. Here we demonstrate a simple technique, which we call ‘push coating’, to produce uniform large-area semiconducting polymer films over a hydrophobic surface with eliminating material loss. We utilize a poly(dimethylsiloxane)-based trilayer stamp whose conformal contact with the substrate enables capillarity-induced wetting of the surface. Films are formed through solvent sorption and retention in the stamp, allowing the stamp to be peeled perfectly from the film. The planar film formation on hydrophobic surfaces also enables subsequent fine film patterning. The technique improves the crystallinity and field-effect mobility of stamped semiconductor films, constituting a major step towards flexible electronics production.

Silver nanocolloid, a dense suspension of ligand-encapsulated silver nanoparticles, is an important material for printing-based device production technologies. However, printed conductive patterns of sufficiently high quality and resolution for industrial products have not yet been achieved, as the use of conventional printing techniques is severely limiting. Here we report a printing technique to manufacture ultrafine conductive patterns utilizing the exclusive chemisorption phenomenon of weakly encapsulated silver nanoparticles on a photoactivated surface. The process includes masked irradiation of vacuum ultraviolet light on an amorphous perfluorinated polymer layer to photoactivate the surface with pendant carboxylate groups, and subsequent coating of alkylamine-encapsulated silver nanocolloids, which causes amine–carboxylate conversion to trigger the spontaneous formation of a self-fused solid silver layer. The technique can produce silver patterns of submicron fineness adhered strongly to substrates, thus enabling manufacture of flexible transparent conductive sheets. This printing technique could replace conventional vacuum- and photolithography-based device processing.

We report the structural, electronic, and field-effect transistor characteristics of a series of molecular donor–acceptor charge-transfer (CT) compounds composed of 2,7-dialkyl[1]benzothieno[3,2-b][1]benzothiophenes (diC_n-BTBT; n = 4, 8, and 12) as donors and optionally fluorinated derivatives of tetracyanoquinodimethane (F_mTCNQ; m = 0, 2, and 4) as acceptors. (diC_n-BTBT)(F_mTCNQ) form isomorphous layered crystalline structures consisting of alternating π-conjugated layers and alkyl chain layers, irrespective of the length of the alkyl chains. The compounds exhibit unique double-peaked CT absorption-band features that are polarized along the donor–acceptor interaction. Field-effect transistors based on these single crystals show a relatively high field-effect mobility (0.4 cm² V⁻¹ s⁻¹), the p- and n-type operation of which can be tuned by altering the fluorine substitution in TCNQ.