Piezotronics and piezo-phototronics for adaptive electronics and optoelectronics

Low-dimensional piezoelectric semiconductor nanomaterials, such as ZnO and GaN, have superior mechanical properties and can be integrated into flexible devices that can be subjected to large strain. More importantly, the coupling between piezoelectric polarization and semiconductor properties (for example, electronic transport and photoexcitation) in these materials gives rise to unprecedented device characteristics. This has increased research interest in the emerging fields of piezotronics and piezo-phototronics, which offer new means of manipulating charge-carrier transport, generation, recombination or separation in the controlled operation of flexible devices through the application of external mechanical stimuli. We review the recent progress in advancing our fundamental understanding and in realizing practical applications of piezotronics and piezo-phototronics, and provide an in-depth discussion of future research directions.