Ultrafast charge transfer in atomically thin MoS2/WS2 heterostructures

Abstract

Van der Waals heterostructures have recently emerged as a new class of materials, where quantum coupling between stacked atomically thin two-dimensional layers, including graphene, hexagonal-boron nitride and transition-metal dichalcogenides (MX2), give rise to fascinating new phenomena. MX2 heterostructures are particularly exciting for novel optoelectronic and photovoltaic applications, because two-dimensional MX2 monolayers can have an optical bandgap in the near-infrared to visible spectral range and exhibit extremely strong light-matter interactions. Theory predicts that many stacked MX2 heterostructures form type II semiconductor heterojunctions that facilitate efficient electron-hole separation for light detection and harvesting. Here, we report the first experimental observation of ultrafast charge transfer in photoexcited MoS2/WS2 heterostructures using both photoluminescence mapping and femtosecond pump-probe spectroscopy. We show that hole transfer from the MoS2 layer to the WS2 layer takes place within 50 fs after optical excitation, a remarkable rate for van der Waals coupled two-dimensional layers. Such ultrafast charge transfer in van der Waals heterostructures can enable novel two-dimensional devices for optoelectronics and light harvesting.

Booming Development of Group IV–VI Semiconductors: Fresh Blood of 2D Family

“…Van der Waals (vdW) heterostructures composed of 2D layered materials have been attempted intensively recently due to the novel physical properties covering a wide range of electronic, optical, and optoelectronic systems 198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242. Jo and co‐workers130 synthesized polymorphic 2D tin‐sulfides of either p‐type SnS or n‐type SnS 2 via adjusting hydrogen during the process.…”

Photogating in Low Dimensional Photodetectors

“…Responsivity and response time of part current state‐of‐the‐art low dimensional photodetectors 17, 31, 32, 39, 40, 44, 47, 67, 99, 100, 101, 102, 103, 104. The blue line represents a typical magnitude order of GBP for traditional high‐performance thin‐film photodetectors.…”

Ultrahigh, Ultrafast, and Self‐Powered Visible‐Near‐Infrared Optical Position‐Sensitive Detector Based on a CVD‐Prepared Vertically Standing Few‐Layer MoS2/Si Heterojunction

“…However, pure MoS 2 ‐based optoelectronic devices are usually limited to infrared light detection and lower photoelectric conversion efficiency (PCE) because of the direct band gap of 1.8 eV for single‐layered MoS 2 sheet5, 6 and the picosecond ultrashort carrier lifetime 13, 14. To conquer the drawbacks of wavelength and lifetime limitations, van der Waals heterostructures,15 or lateral heterostructures,16, 17 which are made by stacking a monolayer on the top of another monolayer or a few‐layer crystal or controlled by epitaxial growth of lateral heterojunction, are developed and show great potential for designing high‐performance 2D material‐based photodetectors owing to the combined advantages and synergetic effects of different 2D materials with various band gaps and work functions,18, 19, 20 and the ultrafast layer‐to‐layer transfer speed of carriers 21. To date, various van der Waals heterostructures and lateral heterostructures have been prepared and successfully applied in photodetectors,17, 22 field‐effect transistors,23 photocatalysts,24 and solar cells 16, 25.…”