NEWS OF THE WEEK
INDIUM FIX FOR THIN-FILM ELECTRONICS in nanocrystal-based substances
T
O BUILD COMPONENTS for improved light-
emitting diodes, solar cells, and other electronics, engineers want to use flexible thin films made from semiconductor nanocrystals. Many of these materials unfortunately pick up performancedwindling defects when exposed to air or solvent, making them incompatible with large-scale fabrication methods. A new treatment infusing the films with indium fixes the problem and could help move nanocrystal-based electronics out of the lab and into broad commercial applications (ACS Nano 2013, DOI: 10.1021/nn403752d). A team led by Cherie R. Kagan of the University of Pennsylvania developed the repair technique while working with cadmium selenide nanocrystals, one of the most intensely studied types of nanocrystals. The materials are already used in a few commercial applications. The company QD Vision, for example, has partnered with Sony to sell a CdSe-based display that produces a greater color gamut than is possible with traditional displays. Nanocrystals are favored materials in electronics because their high surface-area-to-volume ratio enhances their reactivity. But that reactivity typically is shortlived—exposure to air and solvents leads to surface defects that ultimately impede performance. Engineers must fabricate devices with the materials under an inert atmosphere and in dry conditions, which often aren’t compatible with large-scale fabrication techniques.
Kagan’s group thought it could fix the defects with indium, a metal commonly used to dope electronic materials to improve their performance. They envisioned that the indium atoms would bind with the films’ surfaces, replacing oxygen and other molecules responsible for the defects. “If you think of a defect as a hole you have to plug,” Kagan says, “the indium comes in and fills that spot.” The treatment step is simple: The team evaporates indium metal in the presence of the nanocrystal thin films and then heats the films. Thin-film transistors made using CdSe and infused with indium outperformed untreated transistors in a number of electrical performance tests. For example, electron mobility in the treated films was about 50 times greater than in the untreated ones. On the basis of data from voltammetry and ultraviolet-visible spectroscopy, the researchers concluded that the indium treatment repairs the thin films by forcing oxygen and water molecules to desorb from the films’ surfaces. Kagan says future work will include using the indium fix with more complex circuitry and using nanocrystals other than CdSe. Prior to this work, says Dmitri V. Talapin, a nanomaterials chemist at the University of Chicago, it was unclear whether nanocrystal-based devices could move beyond a lab curiosity and into real-world applications. “This work convincingly shows that these things can operate in air,” he says.—KATE GREENE, special to C&EN
This array of nanocrystal transistors performs better after an indium treatment fixes defects caused by exposure to air.
ACS NANO
MATERIALS: Metal repairs defects
SCIENTIFIC PUBLISHING Phillip Savage named editor of Industrial & Engineering Chemistry Research The next editor-in-chief of the American Chemical Society journal Industrial & Engineering Chemistry Research will be Phillip E. Savage, a chemical engineering professor at the University of Michigan, Ann Arbor. I&EC Research publishes industrial and academic research in applied chemistry and chemical engineering, with a focus on fundamental research as well as processes and products. ACS, which also publishes C&EN, made the announcement last week. Currently an associate editor of I&EC
Research, Savage will begin his editorship in January 2014, succeeding Donald R. Paul, a chemical engineering professor at the University of Texas, Austin. Paul has headed the journal since 1986. “We are delighted to welcome Phil Savage as the new editor-in-chief of I&EC Research,” says Susan King, senior vice president of the ACS Journals Publishing Group. “His impressive vision for the journal, as well as his vast experience and many diverse achievements in chemical engineering, make him an excellent choice to succeed Don Paul.”
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King offers thanks to Paul “for over a quarter-century dedicated to serving the industrial and engineering chemistry community and for helping to position I&EC Research among the foremost journals in its field.” In his research, Savage focuses on use of water and supercritical fluids for sustainable production of chemicals, materials, and energy. He holds a B.S. from Pennsylvania State University and a Ph.D. from the University of Delaware, both in chemical engineering.—SUSAN AINSWORTH
