A series of ten 2-naphthyl and 2-anthrylbithiophene derivatives with electron acceptor groups were synthesised using the Negishi or Suzuki cross-coupling reaction as a key step. We present a comparison of theoretical and experimental values of the LUMO and gap energies of these derivatives and the effect of the various electron-withdrawing groups on their optical and electrochemical properties. DFT-calculated frontier orbital energy differences have shown a trend following the experimentally determined values. The participation of the electron-withdrawing group in π-conjugation decreases the LUMO level and narrows the energy gap in the order of perfluoroalkyl, acyl, perfluoroacyl, nitro ≈ dicyanovinyl in both series. TD-DFT calculations allowed better understanding of electronic transitions. X-ray structure analysis of naphthalene hexanoyl and perfluorooctanoyl derivatives revealed their herringbone or sandwich herringbone molecular packing, respectively, having a planar naphthalene-bithiophene moiety with opposite (s-trans vs. s-cis) conformation of bithiophene.

We hereby report a successful design strategy for n-type semiconductor materials based on an analogy with efficient p-type semiconductors, by introducing electron-withdrawing groups while maintaining the symmetry of the molecules upon omitting one thiophene unit on each side of the oligoaryl core. Two series of dithienylnaphthalenes and quaterthiophenes substituted with various electron-withdrawing groups have been synthesised using Suzuki or Stille cross-coupling, and Knoevenagel condensation as key steps. The comparison of theoretical and experimental molecular properties related to the effect of electron-withdrawing groups is presented. Both the DFT-calculated and experimentally determined values of the energy gap between frontier orbitals have shown a decreasing trend in the order of perfluoroalkyl, acyl, perfluoroacyl, nitro, alkyldicyanovinyl and perfluoroalkyldicyanovinyl in both series. The X-ray analysis of five derivatives revealed almost planar geometry of the oligoaryl core with a herringbone or lamellar packing motif. The crystal structures of quaterthiophenes exhibited an s-cis conformation between the outer thiophenes in the crystals, in contrast to the theoretical prediction. Carbonyl-based compounds showed n-type behaviour as an active layer in OFET devices with an electron mobility of up to 0.57 cm² V⁻¹ s⁻¹.

A series of bithienyl-terminated surfactants with various alkyl chain lengths (from C8 to C13) and phosphono or chlorodimethylsilyl anchoring groups were synthesized by palladium-catalyzed hydrophosphonation, or platinum-catalyzed hydrosilylation as a key step. Surfactants were tested in pentacene or α-sexithiophene-based organic field-effect transistors (OFETs) for the modification of the dielectric surface. The studied surfactants increased the effective mobility of the α-sexithiophene-based device by up to one order of magnitude. The length of alkyl chain showed to be significant for the pentacene-based device, as the effective mobility only increased in the case of dielectric modification with bithienylundecylphosphonic acid. AFM allowed a better understanding of the morphology of semiconductors on bare SiO₂ and surfaces treated with bithienylundecylphosphonic acid.

Oligothiophenes and their functionalized derivatives have been shown to be a viable option for high-performance organic electronic devices. The functionalization of oligothiophene-based materials allows further tailoring of their properties for specific applications. We have synthesized a new thiophene-based molecule 1-[5′-(2-naphthyl)-2,2′-bithiophen-5-yl]hexan-1-one (NCOH), and we have studied the optical and structural properties of NCOH thin films. NCOH is a highly substituted member of the oligothiophene family, designed to improve its molecular stacking, where the presence of an electron-withdrawing group enhances its electron transport capabilities. Employing in situ and time-resolved grazing-incidence wide-angle X-ray scattering (GIWAXS) measurements, we determined the NCOH thin film crystallographic structure and its evolution starting from the early stages of the film growth. We observed strong optical anisotropy resulting from a highly oriented crystallographic structure. Additionally, we investigated the substrate-induced changes of the molecular orientation utilizing the few-layer MoS₂ with different orientations of the atomic layers. This study, with its primary focus on the fundamentally important n-type molecular semiconductor, contributes to the field of organic-based (opto-)electronics.

Synthetic options for conversion of indeno[2,1‐c]fluorene‐5,8‐diones into larger polyaromatic compounds with extended π‐conjugated systems were explored. The crucial two‐fold transformation of the five‐membered ketone moieties of indeno[2,1‐c]fluorene‐5,8‐diones was based either on a one‐carbon homologation or on a ring‐expansion reaction which eventually enabled syntheses of compounds possessing substituted tribenzo[a,e,l]indeno[1,2,3‐hi]acephenanthrylenes and [5]helicenes scaffolds. The former was prepared by using a reaction sequence based on Ramirez olefination, intramolecular Heck reaction, and intermolecular Suzuki‐Miyaura cross‐coupling, whereas the latter utilized a sequence comprising Büchner−Curtius−Schlotterbeck reaction and intermolecular Suzuki‐Miyaura cross‐coupling. Scholl reaction of selected [5]helicenes yielded planarized polyaromatic compounds with the tribenzo[a,e,l]indeno[1,2,3‐hi]acephenanthrylene scaffold. Where possible, structures of products were confirmed by X‐ray diffraction analyses. Photophysical properties were determined as well.

Defects in organic semiconductors can significantly affect the functionality of organic photonic devices. However, unlike inorganic materials, they are still little researched. This article investigates structural defect states in the bandgap of n-type small molecular semiconductor 2,2’-{[5,5’-(Naphthalene-2,6-diyl)bis(thiophene-5,2-diyl)]bis(2,2,2-trifluoroethan-1-yl-1-ylidene)}dimalononitrile (TNT-FEC). Using the energy-resolved electrochemical impedance spectroscopy (ER-EIS), we mapped the presence of defect states in this material, and by comparing measurements in the solution and the film, we identified the structural ones. Furthermore, we investigated the influence of the substrate on defect formation. Finally, using DFT and DFTB calculations, we analyzed the possibility of the conformers’ presence, which can influence the structural properties of thin films. The combination of experimental and theoretical approaches in the analysis of defect states has been shown as suitable for studying structural defects’ presence in the thin films of organic semiconductors.