Insulators or semiconductors that lack inversion symmetry exhibit a piezoelectric eect, which is an electromechanical coupling that allows energy conversion from mechanical to electrical , and vice versa. This eect is used in many important applications such actuators, sensors, and transducers . Current trends in miniaturization of devices require piezoelectricity at the nanoscale. Being at most a few atomic-layers thick, 2D piezoelectrics have potential for miniaturizing these electromechanical devices down to nanoscale. Moreover, compared with 3D piezoelectrics (e.g., bulk crystals or thin-lms), few layered (typically 1-3 layers) piezoelectric materials can generally handle larger deformation . Importantly, nowadays these 2D materials can be grown in good crystalline quality. Hence, 2D piezoelectrics become promising for self-powered, exible, and wearable nano-devices. These 2D piezoelectrics can also nd interesting applications in new type of electronics such as piezotronics where the electronic band gap is controlled by the electric potential steaming from piezoelectricity and in piezo-photonics , where light is coupled with the piezoelectrically induced charges. For example, it has been predicted that the performance of MoS 2based solar cells can be enhanced by the coupling of semiconducting and piezoelectric properties .