Extremely Low Dark Current MoS₂ Photodetector via 2D Halide Perovskite as the Electron Reservoir

Toward pursuing high-performance photodetectors based on 2D transition metal dichalcogenides (TMDs) such as molybdenum disulfide (MoS₂), it is desirable to reduce the high dark current and sluggish response time. Here, in multilayer MoS₂-based photodetectors, a 2D halide perovskite, (C₆H₅C₂H₄NH₃)₂PbI₄ ((PEA)₂PbI₄), is introduced as a bifunctional material: both as electron reservoir to reduce free carriers and passivation agent to passivate defects. Surprisingly, dark current is suppressed by six orders of magnitude after coating a (PEA)₂PbI₄ thin layer onto pristine MoS₂ photodetector, with the dark current decreased to 10⁻¹¹ A. This huge reduction of dark current suggests an efficient interlayer charge transfer from MoS₂ to (PEA)₂PbI₄, which is further verified by photoluminescence quenching phenomenon. It indicates that (PEA)₂PbI₄ serves as electron reservoir to reduce carrier density of MoS₂, resulting in ultrahigh detectivity (1.06 × 10¹³ Jones). Moreover, the response speed is also accelerated by more than 100-fold due to passivation by 2D perovskite. In addition, it is found that this type of photodetectors can further work at self-power mode (with the bias of 0 V). Therefore, the strategy of applying 2D perovskite on the surface of TMDs provides a novel way to fabricate high-performance photodetectors.