1901402 (1 of 8) © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.advopticalmat.de FULL PAPER Extremely Low Dark Current MoS 2 Photodetector via 2D Halide Perovskite as the Electron Reservoir Haoliang Wang, Xudong Wang, Yan Chen, Shukui Zhang, Wei Jiang, Xin Zhang, Jiajun Qin, Jiao Wang, Xiaoguo Li, Yiyi Pan, Fengcai Liu, Zejiao Shi, Haijuan Zhang, Luqi Tu, Hailu Wang, Huabao Long, Dapeng Li, Tie Lin, Jianlu Wang,* Yiqiang Zhan,* Hong Shen,* Xiangjian Meng, and Junhao Chu DOI: 10.1002/adom.201901402 1. Introduction 2D transition metal dichalcogenides (TMDs) have attracted enormous attention due to their novel and outstanding optoe- lectronic properties in the past few years. [1] Among them, MoS 2 has been extensively studied because of its atomic-thin struc- ture, high quantum efficiency, decent carrier mobility, and thickness-dependent tunable bandgap. [2–4] With these novel properties, MoS 2 is considered to be a competitive candidate for the application in the next-generation photodetectors. Early works revealed capability of dif- ferent layers MoS 2 for the photon detec- tion, [5–8] and proved that the bandgap of MoS 2 was highly related to the thickness at a variable range from 1.2 to 1.8 eV. [9,10] Multilayer MoS 2 flakes have a narrower bandgap and could provide a wider spec- tral detection range (from ultraviolet (UV) to near-infrared (NIR)) than mon- olayer MoS 2 . For the light detection application, a wider spec- trum response means the ability to be compatible with more complicate light-detection scenarios. In addition, it is gener- ally believed thick multilayer MoS 2 gains better light absorp- tion compared to atomic-thin monolayer MoS 2 . [1,4–6] The wider detection range and better light absorption ability have made the multilayer MoS 2 a great candidate for a broad detec- tion range, high-performance photodetector. However, there are still some drawbacks that limit the further applications of multilayer MoS 2 photodetectors. Compared to monolayer MoS 2 , multilayer MoS 2 has better electric conductance, which results in a large dark current. [6,7] Dark current, usually consid- ered as noise, is an important parameter to evaluate the per- formance of a photodetector. [2] Almost all the main parameters such as responsivity (R), detectivity (D*), and photoswitching on/off ratio are related to the dark current. Large dark current in multilayer MoS 2 photodetectors became a major issue and hindered its further development. To suppress the dark cur- rent, the traditional method is to fabricate the three-terminal photodetectors (source, drain, and gate) and apply the gate bias to control the carrier density in the channel. [5–8] But com- pared to two-terminal device, the three-terminal devices make Toward pursuing high-performance photodetectors based on 2D transition metal dichalcogenides (TMDs) such as molybdenum disulfide (MoS 2 ), it is desirable to reduce the high dark current and sluggish response time. Here, in multilayer MoS 2 -based photodetectors, a 2D halide perovskite, (C 6 H 5 C 2 H 4 NH 3 ) 2 PbI 4 ((PEA) 2 PbI 4 ), 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) 2 PbI 4 thin layer onto pristine MoS 2 photodetector, with the dark current decreased to 10 -11 A. This huge reduction of dark current suggests an effi- cient interlayer charge transfer from MoS 2 to (PEA) 2 PbI 4 , which is further verified by photoluminescence quenching phenomenon. It indicates that (PEA) 2 PbI 4 serves as electron reservoir to reduce carrier density of MoS 2 , resulting in ultrahigh detectivity (1.06 × 10 13 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. Dr. H. Wang, Dr. X. Wang, Dr. Y. Chen, Dr. S. Zhang, Dr. W. Jiang, Dr. L. Tu, Dr. H. Wang, Prof. T. Lin, Prof. J. Wang, Prof. H. Shen, Prof. X. Meng, Prof. J. Chu State Key Laboratory of Infrared Physics Shanghai Institute of Technical Physics Chinese Academy of Sciences 500 Yu Tian Road, Shanghai 200083, China E-mail: jlwang@mail.sitp.ac.cn; hongshen@mail.sitp.ac.cn Dr. X. Zhang Academy for Engineering and Technology Fudan University Shanghai 200433, China Dr. J. Qin, Prof. J. Wang, Dr. X. Li, Dr. Y. Pan, Dr. F. Liu, Dr. Z. Shi, Dr. H. Zhang, Prof. Y. Zhan Center of Micro-Nano System SIST Fudan University Shanghai 200433, China E-mail: yqzhan@fudan.edu.cn Prof. H. Long, Prof. D. Li Shanghai Aerospace Control Technology Institute 1555 Zhong Chun Road, Shanghai 201109, China The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adom.201901402. Adv. Optical Mater. 2020, 1901402