ИСТИНА

Performance of organic field-effect transistors (OFETs) strongly depends on the organic semiconducting materials structure, their purity and morphology. On the one hand, it is well-known that charge carriers in the OFETs are induced on the interface between dielectric and organic semiconducting layers by external electric field from the gate electrode. Hence, most of the charges are passed through the first monolayer of the organic semiconductor, while the following 2-3 monolayers improves the field-effect mobility somewhat further if the first monolayer is not perfect. On the other hand, mobility in OFETs is affected by the degree of ordering of organic semiconductors, with the highest mobility reported for monocrystalline OFETs. Hence, an ideal OFET should be ultrathin and monocrystalline. Monolayer OFETs are particularly interesting due to low consumption of organic semiconductors as well as their unique sensitivity to the environment, which allows creation of ultrasensitive gas sensors.[1] Monolayer OFETs can be prepared either by physisorption or by self-assembly of various conjugated oligomers (see Figure). The former can be grown from solution of conjugated thiophene or thiophene-phenylene oligomers by drop or spin casting with subsequent slow solvent evaporation, leading to single-crystal monolayers of unprecedented structural order, which demonstrated excellent performance in OFETs.[2] The latter may be easily prepared from highly stable organosilicon derivatives of organic semiconductors,[3] capable to self-assembly on the water-air interface, which allows fabrication of monolayer OFETs by Langmuir-Blodgett (LB) or Langmuir-Shaeffer (LS) techniques.[4] Investigation of their electrical characteristics in various gas environment suggested their application as ultrasensitive gas sensors capable to detect up to hundreds ppb of hydrogen sulfide or ammonia, which pave the way of the development of an electronic nose based on this technology.[5] Figure: Examples of chemical structures of organic semiconductors synthesized and investigated in this work. Synthetic work was made in the framework of Leading Science School supported by Russian Ministry of Science and Higher Educatiuon (grant NSh-5698.2018.3). Investigation of single crystal OFETs was supported by RSF (grant 18-12-00499), preparation and measurements of monolayer LS OFETs was supported by RSF (grant 19-73-30028). 1. A.S. Sizov, E.V. Agina, S.A. Ponomarenko, Russ. Chem. Rev. 87, 1226 (2018) 2. V.V. Bruevich at. al., ACS Appl. Mater. Interfaces 11, 6315 (2019) 3. O.V. Borshchev et. al., Chem. Comm. 53, 885 (2017) 4. A.A. Trul et. al., J. Mater. Chem. C 6, 9649 (2018) 5. A.S. Sizov at. al., ACS Appl. Mater. Interfaces 10, 43831 (2018)