Three new fused thiophene semiconductors, end-capped with diperfluorophenylthien-2-yl (DFPT) groups (DFPT-thieno[2′,3′:4,5]thieno[3,2-b]thieno[2,3-d]thiophene (TTA), DFPT-dithieno[2,3-b:3′,2′-d]thiophenes (DTT), and DFPT-thieno[3,2-b]thiophene (TT)), are synthesized and characterized in organic thin film transistors. Good environmental stability of the newly developed materials is demonstrated via thermal analysis as well as degradation tests under white light. The molecular structures of all three perfluorophenylthien-2-yl end-functionalized derivatives are determined by single crystal X-ray diffraction. DFPT-TTA and DFPT-TT exhibit good n-type TFT performance, with mobilities up to 0.43 and 0.33 cm² V⁻¹ s⁻¹, respectively. These are among the best performing n-type materials of all fused thiophenes reported to date. The best thin film transistor device performance is achieved via an n-octadecyltrichlorosilane dielectric surface treatment on the thermally grown Si/SiO₂ substrates prior to vapor-phase semiconductor deposition. Within the DFPT series, carrier mobility magnitudes depend strongly on the semiconductor growth conditions and the gate dielectric surface treatment.

The nature of charge transport and local structure are investigated in amorphous indium oxide-based thin films fabricated by spin-coating. The In–X–O series where X = Sc, Y, or La is investigated to understand the effects of varying both the X cation ionic radius (0.89–1.17 Å) and the film processing temperature (250–300 °C). Larger cations in particular are found to be very effective amorphosizers and enable the study of high mobility (up to 9.7 cm² V⁻¹ s⁻¹) amorphous oxide semiconductors without complex processing. Electron mobilities as a function of temperature and gate voltage are measured in thin-film transistors, while X-ray absorption spectroscopy and ab initio molecular dynamics simulations are used to probe local atomic structure. It is found that trap-limited conduction and percolation-type conduction mechanisms convincingly model transport for low- and high-temperature processed films, respectively. Increased cation size leads to increased broadening of the tail states (10–23 meV) and increased percolation barrier heights (24–55 meV) in the two cases. For the first time in the amorphous In–X–O system, such effects can be explained by local structural changes in the films, including decreased In–O and In–M (M = In, X) coordination numbers, increased bond length disorder, and changes in the MO _x polyhedra interconnectivity.

The molecular packing motifs within crystalline domains should be a key determinant of charge transport in thin-film transistors (TFTs) based on small organic molecules. Despite this implied importance, detailed information about molecular organization in polycrystalline thin films is not available for the vast majority of molecular organic semiconductors. Considering the potential of fused thiophenes as environmentally stable, high-performance semiconductors, it is therefore of interest to investigate their thin film microstructures in relation to the single crystal molecular packing and OTFT performance. Here, the molecular packing motifs of several new benzo[d,d′]thieno[3,2-b;4,5-b′]dithiophene (BTDT) derivatives are studied both in bulk 3D crystals and as thin films by single crystal diffraction and grazing incidence wide angle X-ray scattering (GIWAXS), respectively. The results show that the BTDT derivative thin films can have significantly different molecular packing from their bulk crystals. For phenylbenzo[d,d′]thieno[3,2-b;4,5-b′]dithiophene (P-BTDT), 2-biphenylbenzo[d,d′]thieno-[3,2-b;4,5-b′]dithiophene (Bp-BTDT), 2-naphthalenylbenzo[d,d′]thieno[3,2-b;4,5-b′]dithiophene (Np-BTDT), and bisbenzo[d,d′]thieno[3,2-b;4,5-b′]dithiophene (BBTDT), two lattices co-exist, and are significantly strained versus their single crystal forms. For P-BTDT, the dominance of the more strained lattice relative to the bulk-like lattice likely explains the high carrier mobility. In contrast, poor crystallinity and surface coverage at the dielectric/substrate interface explains the marginal OTFT performance of seemingly similar PF-BTDT films.