Hongxia Xi

Novel copolymers incorporating dithieno[3,2-b:2′,3′-d]thiophene moieties for air-stable and high performance organic field-effect transistors

A series of semiconducting copolymers incorporating dithieno[3,2-b:2′,3′-d]thiophene moieties in the polythiophene backbone were synthesized. The resulting four copolymers are found to have large band gap (∼ 2.5 eV) and large ionization potential (−5.1 eV). Organic field-effect transistors were fabricated by spin-coating polymer solutions onto OTS-modified SiO2/Si substrates with top-contact configuration. The best resulting hole mobility afforded was 0.028 cm2V−1 s−1 with an on/off ratio of 2 × 104 and a threshold voltage of about −18.9 V in the saturation regime. Furthermore, all the devices exhibited high environmental stability against oxygen doping and relatively high ambient humidity (∼30%).

Blending induced stack-ordering and performance improvement in a solution-processed n-type organic field-effect transistor

The mobilities of the solution-processed n-type organic semiconductor, N,N′-di((Z)-9-octadecene)-3,4,9,10-perylene tetracarboxylic diimide (PTCDI-e), were dramatically improved (up to 30 times) by blending with electron donors. The reason can be assigned to the facilitated charge transport due to the increased stack-ordering and crystallinity of the spin-coated thin films after blending. This provides a new way to enhance the performance of existing organic semiconductors by intentional blending.

6H-Pyrrolo[3,2-b:4,5-b′]bis[1,4]benzothiazines: facilely synthesized semiconductors for organic field-effect transistors

6H-Pyrrolo[3,2-b:4,5-b′]bis[1,4]benzothiazine (PBBTZ, 1) and its two 6-substituted derivatives (2 and 3) were conveniently synthesized. Their optical properties were studied by UV-vis and fluorescence spectroscopy, and electrochemical properties were investigated by cyclic voltammetry (CV). Good thermal stability was observed by thermogravimetric analysis. X-Ray analysis revealed a coplanar structure and a column stacking in the single crystal of compound 1. OFET measurements showed that 1–3 were p-type semiconductors. The performance of these devices displayed good reproducibility at ambient conditions. When devices containing 1 were fabricated on OTS-treated SiO2/Si substrates at 60 °C, the best performance was achieved with the average hole mobility as high as 0.34 cm2V−1 s−1 and the on/off ratio about 106–107. This performance resulted from the well-ordered molecular packing as revealed by XRD and AFM analysis.

A New “Bones/Muscles” Strategy for Preparing Highly Conducting Single‐Walled Carbon‐Nanotube Films with Ultrahigh Transparency

Exploring the potential application of single-walled carbon nanotubes (SWNTs) as buildingblocks in future electronics has attracted increasing attention in recent years. However, devices based on an individual tube, though promising in nanoelectronics, have amajor drawback of irreproducibility. SWNTfilms, becauseof their optical transparency, flexibility, and good electrical properties, have been suggested for the conducting channels of transparent field-effect transistors (FETs) or conducting coatings as an alternative to indium tin oxide (ITO) glass. One of the promising applications of SWNT transparent conducting films (TCFs) is as a transparent electrode for touch panels ordisplays. For theseapplications, a transmittanceof the conducting coating together with the substrate that is higher than 85%(550 nm) is highly recommended.The transmittances of glass, quartz, andpoly(ethylene terephthalate) (PET),which aregenerallyusedas the substrates, areabout 92, 93, and91%in the visible region, respectively. With the consideration of the substrates’ contribution to transmittance loss, the transmittance of the SWNT film without substrate (WO/S) should be higher than 94% (550 nm) when a PET substrate is used. We note that the transparency is more important than sheet resistance if the sheet resistance is in an acceptable region