Multiple Effects of Inhomogeneous Strain Field on Carrier Distribution in Bending 2D Materials

It is critical to investigate optoelectronic properties in bending 2D materials, especially for inhomogeneous strain field (iHSF), for application of flexible nanoelectronics. Using first-principles calculations, we find there are multiple effects of iHSF on charge distribution in g-C3N4 nanosheets and black phosphorus nanoribbons (BPNRs). On the one hand, in rippled g-C3N4, the valence band maximum (VBM) and conduction band minimum (CBM) of the whole structure are spatially separated, thus the photogenerated electrons and holes are driven to different regions, respectively. This indicates the rippled g-C3N4, with potential advantage of good efficiency of electron-hole separation, is a flexible and promising platform for metal-free photocatalytic water splitting. On the other hand, the iHSF forms multiple exciton funnels in BPNRs. We find the type of funnels (spatial distribution and motion of excitons) can be tuned by changing the intensity and sign (tensile or compressed) of the strain field, thickness and periodicity (zigzag or armchair) of BPNRs. By forming different funnels, the excitons are able to be accumulated in unstrained, tensile or compressed regions, which enriches the means of controlling excitons for photo-detecting or photo-emitting.