Single crystals of thiophene−phenelyne co-oligomers (TPCOs) have previously shown their potential for organic optoelectronics. Here we report on solution growth of large-area thin single-crystalline films of TPCOs at the gas−liquid interface by using solvent−antisolvent crystallization, isothermal slow solvent evaporation, and isochoric cooling. The studied co-oligomers contain identical conjugated core (5,5′diphyenyl-2,2′-bithiophene) and different terminal substituents, fluorine, trimethylsilyl, or trifluoromethyl. The fabricated films are molecularly smooth over areas larger than 10 × 10 μm 2 , which is of high importance for organic field-effect devices. The low-defect structure of the TPCO crystals is suggested from the monoexponential kinetics of the PL decay measured in a wide dynamic range (up to four decades) and from low crystal mosaicity assessed by microfocus X-ray diffraction. The TPCO crystal structure is solved using a combination of X-ray and electron diffraction. The terminal substituents affect the crystal structure of TPCOs, bringing about the formation of a noncentrosymmetric crystal lattice with a crystal symmetry Cc for the bulkiest trimethylsilyl terminal groups, which is unusual for linear conjugated oligomers. Comparing the different crystal growth techniques, it is concluded that the solvent−antisolvent crystallization is the most robust for fabrication of single-crystalline TPCOs films. The possible nucleation and crystallization mechanisms operating at the gas−solution interface are discussed.

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Thiophene-phenylene co-oligomers (TPCOs) are among the most promising materials for organic light emitting devices. Here we report on record high among TPCO single crystals photoluminescence quantum yield reaching 60%. The solution-grown crystals are stronger luminescent than the vapor-grown ones, in contrast to a common believe that the vapor-processed organic electronic materials show the highest performance. We also demonstrate that the solution-grown TPCO single crystals perform in organic field effect transistors as good as the vapor-grown ones. Altogether, the solution-grown TPCO crystals are demonstrated to hold great potential for organic electronics.

Self-assembly of highly soluble water-stable tetramethyldisiloxane-based dimer of α,α'-dialkylquaterthiophene on the water-air interface was investigated by Langmuir, grazing incidence X-ray diffraction, and X-ray reflectivity techniques. The conditions for formation of very homogeneous crystalline monolayer Langmuir-Blodgett (LB) films of the oligomer were found. Monolayer organic field-effect transistors (OFETs) based on these LB films as a semiconducting layer showed hole mobilities up to 3 × 10(-3) cm(2)/(V s), on-off ratio of 10(5), small hysteresis, and high long-term stability. The electrical performance of the LB films studied is close to that for the same material in the bulk or in the monolayer OFETs prepared from water vapor sensitive chlorosilyl derivatives of quaterthiophene by self-assembling from solution. These findings show high potential of disiloxane-based LB films in monolayer OFETs for large-area organic electronics.

Organic optoelectronics requires materials combining bright luminescence and efficient ambipolar charge transport. Thiophene-phenylene co-oligomers (TPCOs) are promising highly emissive materials with decent charge-carrier mobility; however, they typically show poor electron injection in devices, which is usually assigned to high energies of their lowest unoccupied molecular orbitals (LUMOs). A widely used approach to lower the frontier orbitals energy levels of a conjugated molecule is its fluorination. In this study, we synthesized three new fluorinated derivatives of one of the most popular TPCOs, 2,2′-(1,4-phenylene)­bis­[5-phenylthiophene] (PTPTP) and studied them by cyclic voltammetry, absorption, photoluminescence, and Raman spectroscopies. The obtained data reveal a positive effect of fluorination on the optoelectronic properties of PTPTP: LUMO levels are finely tuned, and photoluminescence quantum yield and absorbance are increased. We then grew crystals from fluorinated PTPTPs, resolved their structures, and showed that fluorination dramatically affects the packing motif and facilitates π-stacking. Finally, we fabricated thin-film organic field-effect transistors (OFETs) and demonstrated a strong impact of fluorination on charge injection/transport for both types of charge carriers, namely, electrons and holes. Specifically, balanced ambipolar charge transport and electroluminescence were observed only in the OFET active channel based on the partially fluorinated PTPTP. The obtained results can be extended to other families of conjugated oligomers and highlight the efficiency of fluorination for rational design of organic semiconductors for optoelectronic devices.