Impact of grain boundary on photogalvanic effect in transition metal dichalcogenide monolayer

The photogalvanic effect (PGE) has emerged as a promising mechanism for generating photocurrent in 2D materials with broken inversion symmetry. In this study, we systematically investigate the influence of grain boundaries (GBs) on the performance of self-powered photodetectors based on monolayer molybdenum disulfide (MoS₂) using quantum transport simulations. Under the illumination of linearly polarized light, we focus on six types of GBs along armchair and zigzag directions, composed of 4|8 and 4|4 membered rings. Within the visible light regime, the theoretical results demonstrate pronounced enhancement of PGE photocurrent in MoS₂ monolayer with GBs. The average enhancement ratios for 4|8a/b, 4|8c/d and 4|4a/b GBs are approximately 39, 14, 11, 17, 11 and 22, respectively. The enhancement can be primarily attributed to the reduction of symmetry in the dual-probe device, underscoring the important role of GBs in self-powered 2D photodetectors.