Slashdot Mirror
Nanorods Emit and Detect Light, Could Lead To Displays That Communicate Via Li-Fi (ieee.org)
schwit1 quotes a report from IEEE Spectrum: Ever since 2015 Consumer Electronics Show, quantum dots have been in a market struggle to displace light-emitting diodes (LEDs) as a backlight source for liquid crystal displays (LCDs). Now an advance by a team of researchers from the University of Illinois at Urbana-Champaign, the Electronics and Telecommunications Research Institute in South Korea and Dow Chemical may turn the display market on its head by eliminating the need for backlights in LCD devices. They have produced a LED pixel out of nanorods capable of both emitting and detecting light. In research described in the journal Science, the international team of researchers mixed three types of semiconductors to produce engineered nanorods. "The nanorods contain three different semiconductor materials," explains Shim. "The first semiconductor, which is attached at the tips of the nanorod, is the quantum dot that emits and absorbs visible light." The other two semiconductors are the main body of the rod and the shell around the quantum dot. These components facilitate and control the flow of electrons (negative charges) and holes (positive charges) to and from the quantum dot. The semiconductor materials in the rod and the shell each have a band gap in which no electron states can exist as well as band alignment. With these two semiconductors in contact with the quantum dot, the nanorods are extremely efficient at both emitting and detecting light.
... namely that these nanorods are incredibly small (5 nanometers), such that they can be 'liquefied' and used as "semiconductor paint". So it's primarily a breakthrough in 'scaling down', not multitasking. Conventional LED's have always had the capability to detect light. (Ever hear of 'photo-diodes'?). But exploiting this dual-functionality has always been inefficient, due to the relatively large size of individual LED's (on the order of millimeters).
As stated in TFA:
"Shim concedes that is possible to use a LED light bulb as a light-emitting device or as a light-detecting device. Even more, for thin film inorganic semiconductors this is relatively easy thing to do, and, in fact, sort of similar to what the researchers have done here at the individual nanorod level. But because the researchers have made the LED pixel from this colloidal nanorod, it can be processed in solution and in turn be used to make large arrays of LEDs."