We have fabricated pentacene organic thin film transistors with spin-coated polymer gate dielectric layers, including cross-linked polyvinylphenol and a polyvinylphenol-based copolymer, and obtained devices with excellent electrical characteristics, including carrier mobility as large as 3 ${\mathrm{cm}}^2/\mathrm{V s},$ subthreshold swing as low as 1.2 V/decade, and on/off current ratio of ${10}^5.$ For comparison, we have also fabricated pentacene transistors using thermally grown silicon dioxide as the gate dielectric and obtained carrier mobilities as large as 1 ${\mathrm{cm}}^2/\mathrm{V s}$ and subthreshold swing as low as 0.5 V/decade.

Minimizing losses at interfaces: Among the issues facing the practical use of hybrid organohalide lead perovskite solar cells is the loss of charge carriers at interfaces. Hou et al. show that tantalum-doped tungsten oxide forms almost ohmic contacts with inexpensive conjugated polymer multilayers to create a hole-transporting material with a small interface barrier. This approach eliminates the use of ionic dopants that compromise device stability. Solar cells made with these contacts achieved maximum efficiencies of 21.2% and operated stably for more than 1000 hours. Science , this issue p. 1192

Although transition metal dichalcogenides such as MoS₂ have been recognized as highly potent two-dimensional nanomaterials, general methods to chemically functionalize them are scarce. Herein, we demonstrate a functionalization route that results in organic groups bonded to the MoS₂ surface via covalent C–S bonds. This is based on lithium intercalation, chemical exfoliation and subsequent quenching of the negative charges residing on the MoS₂ by electrophiles such as diazonium salts. Typical degrees of functionalization are 10–20 atom % and are potentially tunable by the choice of intercalation conditions. Significantly, no further defects are introduced, and annealing at 350 °C restores the pristine 2H-MoS₂. We show that, unlike both chemically exfoliated and pristine MoS₂, the functionalized MoS₂ is very well dispersible in anisole, confirming a significant modification of the surface properties by functionalization. DFT calculations show that the grafting of the functional group to the sulfur atoms of (charged) MoS₂ is energetically favorable and that S–C bonds are formed.