Tunable Exciton Funnel using Moire Superlattice in Twisted van der Waals' Bilayer

Technology #17158

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Inventors
Professor Ju Li
Department of Nuclear Science and Engineering, MIT
External Link (li.mit.edu)
Xiaofeng Qian
Department of Nuclear Science and Engineering, MIT
Menghao Wu
Department of Nuclear Science and Engineering, MIT
Managed By
Christopher Noble
MIT Technology Licensing Officer - Clean and Renewable Energy
Patent Protection

Engineered Band Gaps

US Patent Pending US 2017-0014796

Engineered Band Gaps

US Patent 9,484,489
Publications
Tunable Exciton Funnel Using MoiréSuperlattice in Twisted van der Waals Bilayer
Nano Letters, 2014, 14 (9), pp 5350–5357

Applications

An optoelectronic material with a spatially varying bandgap can be applied to a wide range of energy and sensing applications such as photovoltaics, photocatalysis, photodetection, bandpass filters for high-frequency applications, and light-emitting devices.

Problem Addressed

The efficiency of many optoelectronic devices is limited by spectrum loss (i.e. only photons within a specific energy range are useful). By twisting a van der Waals' Bilayer, this technology creates tunable spatially dependent bandgaps that increases the spectrum of useful photons.

Technology

Twisted van der Waals' Bilayers can be achieved with a range of materials (e.g. graphene carbon nitride, gallium sulfide). The materials explicitly explored are Carbon/Boron Nitride (CBN) monolayers synthesized with photolithography. To clearly exhibit the Moiré Pattern, the second layer was rotated by 2.5o. This rotation creates a periodic map of bandgaps over the material. There are distinct gradients and minima that can be used to funnel excitons. For twisted bilayer CBN (tbCBN) these bandgaps ranged from 0.53eV to 1.06eV. This range of bandgaps broadens the useful spectrum for optoelectronics. For example, a traditional photovoltaic cell has one band gap and only photons of that energy are completely absorbed. Therefore, by creating a map of bandgaps across the absorption surface spectrum loss is reduced and the cell is more efficient.  By changing the material and degree of rotation, the bandgap map can be tuned to have specific properties.

Advantages

  • A range of bandgaps over one material
  • Increases efficiency for optoelectronics