Prediction of photogalvanic effect enhancement in Janus transition metal dichalcogenide monolayers induced by spontaneous curling

Enhancement of photogalvanic effect (PGE) in two-dimensional materials is of great importance for nanoscale self-powered optoelectronic devices. In this paper, we systematically investigate the generation of PGE photo-current in six Janus transition metal dichalcogenides (MXY, M = Mo,W, X,Y = S,Se,Te) based on the quantum transport simulations. The proposed photodetectors along zigzag and armchair directions with non-collinear electrodes are built based on spontaneous curvatures of Janus TMDs. The spontaneous curling is induced by the relaxation of intrinsic strain in Janus TMDs and the curvatures are determined by molecular simulations. Vertically illuminated by linearly polarized light, PGE photocurrents can be observed in Janus TMDs with both curled and planar structure. The influences of polarization angle and photon energy on the photocurrents are quantitatively demonstrated. The photocurrents are largely amplified by more than 1 order of magnitude on average in the curled photodetector. This enhancement can be attributed to the device symmetry reduction from the C3v to Cs symmetry. We expect the results can help develop recipes for flexible two-dimensional optoelec-tronic devices.