Nano Focus: Grain size determines nanoscale grain rotation
- PDF / 180,525 Bytes
- 1 Pages / 585 x 783 pts Page_size
- 19 Downloads / 232 Views
otential of the polymer series, a thin-film transistor based on this same blend was also constructed and was found to have a high electron (hole) mobility of 5.1 (3.9) × 10–3 cm2/V/s. One important remaining issue in allpolymer OPV device performance is the optimal morphology of the organic thin film. This can be difficult to control with polymer–polymer blends, which tend to phase separate. As Rafael Verduzco of Rice University notes, the ideal microstructure is still unclear: “You probably want well-defined domains of about 10 nanometers, but recent polymers like PTB7 are challenging this thinking.” Verduzco’s group is investigating an approach in which donor and acceptor monomers are block copolymerized, and self-assemble into block lamellar microdomains approximately 9 nm in size. Using this technique, they have demonstrated an all-polymer OPV device with an efficiency of 3.1%.
Organic electronics are increasingly entering commercial use, and the results of this research are obviously of great interest to Polyera, an Illinoisbased company whose markets include wearable electronics, flexible mobile displays, and disposable electronics for supply-chain tracking (one co-author, Antonio Facchetti, is a co-founder and Chief Scientific Officer; Tobin Marks is the other co-founder). Massachusettsbased Konarka was commercializing fullerene-based OPV cells until its bankruptcy in 2012, a fact that has certainly been noted by other aspiring organic electronics companies. While organic electronics are still not competitive with silicon-based systems for most commercial applications, it is clear that they offer some unique properties and are making good progress in closing the gap. It may not be long until OPV throws the solar market a curve—literally. Colin McCormick
of spherical nickel particles (500 nm, 20 nm, or 3 nm in diameter). According to Bin Chen, lead author and director of the Shanghai Laboratory of HPSTAR (Center for High Pressure and Technology Advanced Research), “We chose platinum and nickel, because both have fcc structures, and both are relatively easy for performing texture analysis. We also had several sizes of nickel to work with.” Much to the surprise of the research team, the texture strength of platinum dropped significantly as the particle size of the nickel media was reduced, even though the same-sized platinum particles were used throughout the experiments. Texture was obvious when 500-nm nickel was used, but a considerable loss in texture was observed with the 20-nm nickel. With 3-nm nickel, almost all of the texture disappears. One possible theory was a lack of sufficient shear stress, but this was ruled out both mathematically and by the observation of curved diffraction lines because the curvatures of the unrolled twodimensional diffraction lines demonstrate the existence of differential/shear stress.
Once the first theory was excluded, said the researchers, it became obvious that an enhanced grain rotation of the large platinum particles within the finer nickel medium caused the reduction i
Data Loading...
