Progress in piezotronics of transition-metal dichalcogenides

The coupling of piezoelectricity and semiconductor materials has given rise to a new discipline, named piezotronics. Compared with traditional bulk semiconductors, two-dimensional (2D) semiconductor materials not only exhibit excellent semiconducting characteristics but also have an outstanding mechanical performance. Since the piezoelectricity of 2D transition-metal dichalcogenides (TMDCs) was first observed experimentally in 2014, many novel piezotronic devices based on these semiconductors have been widely investigated, such as energy harvesters, sensors, photoelectric devices and flexible electronic devices. Here, we review recent progress in the piezotronics of 2D TMDCs, with emphasis on the performance enhancement of strain sensors, humidity sensors and photodetectors via piezotronic modulation. To expand the area of piezotronics, 2D TMDCs are being integrated with other piezoelectric materials. These studies demonstrate that piezotronic devices may have great potential applications in wearable electronics, human-computer interfacing, gas sensing, environmental monitoring and microelectromechanical systems.