A new device made from perovskite — one of a large family of materials defined by their special crystal structure — can be directed in two directions: it can receive optical signals and just as easily transmit them. This means that text and photographs can be wirelessly transmitted from one unit to the other and back again, using two identical units, and can be done in real time.
Perovskites consist of metal and halogen and have proved to be versatile semiconductors that are easy and cheap to manufacture. They also have the useful property of both detecting and emitting light. The development of light-emitting diodes from perovskites has made rapid progress; a perovskite light-emitting diode with an efficiency of 21% was recently developed. Researchers now have developed a perovskite that comprises a light-emitting diode and at the same time, is an excellent photodetector.
All-optical communication requires rapid and reliable photodetectors — devices that capture light and convert it into an electrical signal. Current optical communication systems use photodetectors made from materials such as silicon and indium gallium arsenide. These are, however, expensive and they cannot be used in applications that require low weight, flexibility, or large surfaces.
In order to demonstrate the potential of the diode with double function, the researchers built a monolithic sensor that detects heartbeats in real time and an optical, bidirectional communication system. The tiny unit that can both receive and transmit optical signals provides a unique opportunity to simplify and shrink the functionality of the current optical systems; in particular, given that it can also be integrated with traditional electronic circuits.