A team of MIT researchers has used a novel material that’s just a few atoms thick to create devices that can harness or emit light. This proof-of-concept could lead to ultrathin, lightweight, and flexible photovoltaic cells, light emitting diodes (LEDs), and other optoelectronic devices, they say. Their report is one of three papers by different groups describing similar results with this material, published in the March 9 issue of Nature Nanotechnology. The MIT research was carried out by Pablo Jarillo-Herrero, the Mitsui Career Development Associate Professor of Physics, graduate students Britton Baugher and Yafang Yang, and postdoc Hugh Churchill. The material they used, called tungsten diselenide (WSe2), is part of a class of single-molecule-thick materials under investigation for possible use in new optoelectronic devices — ones that can manipulate the interactions of light and electricity. In these experiments, the MIT researchers were able to use the material to produce diodes, the basic building block of modern electronics....

A new way of making large sheets of high-quality, atomically thin graphene could lead to ultra-lightweight, flexible solar cells, and to new classes of light-emitting devices and other thin-film electronics. The new manufacturing process, which was developed at MIT and should be relatively easy to scale up for industrial production, involves an intermediate “buffer” layer of material that is key to the technique’s success. The buffer allows the ultrathin graphene sheet, less than a nanometer (billionth of a meter) thick, to be easily lifted off from its substrate, allowing for rapid roll-to-roll manufacturing. The process is detailed in a paper published yesterday in Advanced Functional Materials, by MIT postdocs Giovanni Azzellino and Mahdi Tavakoli; professors Jing Kong, Tomas Palacios, and Markus Buehler; and five others at MIT. Finding a way to make thin, large-area, transparent electrodes that are stable in open air has been a major quest in thin-film electronics in recent years, for a variety of applications in optoelectronic devices — things that either emit light, like computer and smartphone screens, or harvest it, like solar cells. Today’s standard for such applications is indium tin oxide (ITO), a material based on rare and expensive chemical elements....

Using only processes found in existing microchip fabrication facilities, researchers at MIT, the University of California at Berkeley, and the University of Colorado have produced a working optoelectronic microprocessor, which computes electronically but uses light to move information. Optical communication could dramatically reduce chips’ power consumption, which is not only desirable in its own right but essential to maintaining the steady increases in computing power that we’ve come to expect. Demonstrating that optical chips can be built with no alteration to existing semiconductor manufacturing processes should make optical communication more attractive to the computer industry. But it also makes an already daunting engineering challenge even more difficult. “You have to use new physics and new designs to figure out how you take ingredients and process recipes that are used to make transistors, and use those to make photodetectors, light modulators, waveguides, optical filters, and optical interfaces,” says MIT professor of electrical engineering Rajeev Ram, referring to the optical components necessary to encode data onto different wavelengths of light, transmit it across a chip, and then decode it. “How do you build all the optics using only the layers out of a transistor? It felt a bit like an episode of ‘MacGyver’ where he has to build an optical network using only old computer parts.”...

Growing up in a small town in Fujian province in southern China, Juejun Hu was exposed to engineering from an early age. His father, trained as a mechanical engineer, spent his career working first in that field, then in electrical engineering, and then civil engineering. “He gave me early exposure to the field. He brought me books and told me stories of interesting scientists and scientific activities,” Hu recalls. So when it came time to go to college — in China students have to choose their major before enrolling — he picked materials science, figuring that field straddled his interests in science and engineering. He pursued that major at Tsinghua University in Beijing. He never regretted that decision. “Indeed, it’s the way to go,” he says. “It was a serendipitous choice.” He continued on to a doctorate in materials science at MIT, and then spent four and a half years as an assistant professor at the University of Delaware before joining the MIT faculty. Last year, Hu earned tenure as an associate professor in MIT’s Department of Materials Science and Engineering....