Understanding the relationship between molecular/macromolecular architecture and organic thin film transistor (TFT) performance is essential for realizing next-generation high-performance organic electronics. In this regard, planar π-conjugated, electron-neutral (i.e., neither highly electron-rich nor highly electron-deficient) building blocks represent a major goal for polymeric semiconductors, however their realization presents synthetic challenges. Here we report that an easily accessible (minimal synthetic steps), electron-neutral thienyl-vinylene (TVT)-based building block having weak intramolecular S···O "conformational locks" affords a new class of stable, structurally planar, solution-processable, high-mobility, molecular, and macromolecular semiconductors. The attraction of merging the weak TVT electron richness with supramolecular planarization is evident in the DFT-computed electronic structures, favorable MO energetics, X-ray diffraction-derived molecular structures, experimental lattice coehesion metrics, and excellent TFT performance. TVT-based polymer TFTs exhibit stable carrier mobilities in air as high as 0.5 and 0.05 cm(2)/V·s (n- and p-type, respectively). All-TVT polymer-based complementary inverter circuitry exhibiting high voltage gains (~50) and ring oscillator circuitry with high f(osc)(~1.25 kHz) is readily fabricated from these materials by simple inkjet printing.

Organic thin film transistor (OTFT) performance is highly materials interface-dependent, and dramatic performance enhancements can be achieved by properly modifying the semiconductor/gate dielectric interface. However, the origin of these effects is not well understood, as this is a classic "buried interface" problem that has traditionally been difficult to address. Here we address the question of how n-octadecylsilane (OTS)-derived self-assembled monolayers (SAMs) on Si/SiO(2) gate dielectrics affect the OTFT performance of the archetypical small-molecule p-type semiconductors P-BTDT (phenylbenzo[d,d]thieno[3,2-b;4,5-b]dithiophene) and pentacene using combined in situ sum frequency generation spectroscopy, atomic force microscopy, and grazing incidence and reflectance X-ray scattering. The molecular order and orientation of the OTFT components at the dielectric/semiconductor interface is probed as a function of SAM growth mode in order to understand how this impacts the overlying semiconductor growth mode, packing, crystallinity, and carrier mobility, and hence, transistor performance. This understanding, using a new, humidity-specific growth procedure, leads to a reproducible, scalable process for highly ordered OTS SAMs, which in turn nucleates highly ordered p-type semiconductor film growth, and optimizes OTFT performance. Surprisingly, the combined data reveal that while SAM molecular order dramatically impacts semiconductor crystalline domain size and carrier mobility, it does not significantly influence the local orientation of the overlying organic semiconductor molecules.

The performance of bottom‐contact thin‐film transistor (TFT) structures lags behind that of top‐contact structures owing to the far greater contact resistance. The major sources of the contact resistance in bottom‐contact TFTs are believed to reflect a combination of non‐optimal semiconductor growth morphology on the metallic contact surface and the limited available charge injection area versus top‐contact geometries. As a part of an effort to understand the sources of high charge injection barriers in n‐channel TFTs, the influence of thiol metal contact treatment on the molecular‐level structures of such interfaces is investigated using hexamethyldisilazane (HMDS)‐treated SiO2 gate dielectrics. The focus is on the self‐assembled monolayer (SAM) contact surface treatment methods for bottom‐contact TFTs based on two archetypical n‐type semiconductors, α,ω‐diperfluorohexylquarterthiophene (DFH‐4T) and N,N′bis(n‐octyl)‐dicyanoperylene‐3,4:9,10‐bis(dicarboximide) (PDI‐8CN2). TFT performance can be greatly enhanced, to the level of the top contact device performance in terms of mobility, on/off ratio, and contact resistance. To analyze the molecular‐level film structural changes arising from the contact surface treatment, surface morphologies are characterized by atomic force microscopy (AFM) and scanning tunneling microscopy (STM). The high‐resolution STM images show that the growth orientation of the semiconductor molecules at the gold/SAM/semiconductor interface preserves the molecular long axis orientation along the substrate normal. As a result, the film microstructure is well‐organized for charge transport in the interfacial region.

Facile one‐pot [1 + 1 + 2] and [2 + 1 + 1] syntheses of thieno[3,2‐b]thieno[2′,3′:4,5]thieno[2,3‐d]thiophene (tetrathienoacene; TTA) semiconductors are described which enable the efficient realization of a new TTA‐based series for organic thin‐film transistors (OTFTs). For the perfluorophenyl end‐functionalized derivative DFP‐TTA, the molecular structure is determined by single‐crystal X‐ray diffraction. This material exhibits n‐channel transport with a mobility as high as 0.30 cm2V−1s−1 and a high on‐off ratio of 1.8 × 107. Thus, DFP‐TTA has one of the highest electron mobilities of any fused thiophene semiconductor yet discovered. For the phenyl‐substituted analogue, DP‐TTA, p‐channel transport is observed with a mobility as high as 0.21 cm2V−1s−1. For the 2‐benzothiazolyl (BS‐) containing derivative, DBS‐TTA, p‐channel transport is still exhibited with a hole mobility close to 2 × 10−3 cm2V−1s−1. Within this family, carrier mobility magnitudes are strongly dependent on the semiconductor growth conditions and the gate dielectric surface treatment.

The molecular packing motifs within crystalline domains should be a key determinant of charge transport in thin-fi lm transistors (TFTs) based on small organic molecules. Despite this implied importance, detailed information about molecular organization in polycrystalline thin fi lms is not available for the vast majority of molecular organic semiconductors. Considering the potential of fused thiophenes as environmentally stable, highperformance semiconductors, it is therefore of interest to investigate their thin fi lm microstructures in relation to the single crystal molecular packing and OTFT performance. have been scrutinized, such assumptions have been proven to sometimes be inaccurate, and it is now known that molecular packing in thin fi lms may differ signifi cantly from that in the bulk crystal structures, especially near the dielectric interface. For example, in thin fi lm form, both tetraceno[2,3-b]thiophene [ 17 ] and pentacene [ 16 ] exhibit a local molecular packing distinctly different from that in the bulk crystal. These observations highlight the necessity of obtaining microstructural details for thin organic fi lms.In this contribution, the molecular packing motifs of fi ve newly synthesized BTDT [ 9 ] derivatives ( Scheme 2 ), are studied both in bulk single crystals and in thin fi lms by single crystal diffraction and grazing incidence wide angle X-ray scattering (GIWAXS). We fi rst introduce the new BTDT molecules and describe their thermal, optical, and electrochemical properties. We then compare the bulk and thin fi lm structures by analyzing single-crystal X-ray diffraction and GIWAXS data. Lastly, the effect of thin fi lm microstructure on TFT performance is discussed. The results indicate that these BTDT derivatives have different molecular packing in thin fi lms versus the bulk crystals. In the case of P-BTDT , Bp-BTDT , Np-BTDT , and BBTDT , it will be seen that two types of lattices coexist, and that these are slightly strained compared to their bulk crystal forms. In contrast, for PF-BTDT fi lms, a single lattice is observed, however, this lattice has no apparent correspondence to the bulk crystal form. For P-BTDT , which yields the best performing TFTs of the series, the dominance of the more strained lattice relative to the bulk-like lattice may explain the excellent charge transport properties. On the other hand, poor crystallinity and poor surface coverage at the substrate interface explains the poor device performance of PF-BTDT fi lms. Results SynthesisDetails of the various BTDT syntheses can be found in the Supporting Information or previous literature. [ 9 ] Briefl y, the derivatives [ 2 , 9-14 ] offer a potential solution to this challenge, owing to their combination of suffi ciently high-lying excited states and high ionization potentials to suppress photo-oxidation, [ 11 ] and bulk single crystal packing motifs which are very similar to that of pentacene. Among organic semiconductor materials for p-channel devices, several fused thiophene derivatives with increased numb...