Near-direct bandgap WSe2/ReS2 type-II pn heterojunction for enhanced ultrafast photodetection and high-performance photovoltaics

Abin Varghese, Dipankar Saha, Kartikey Thakar, Vishwas Jindal, Sayantan Ghosh, Nikhil V. Medhekar, Sandip Ghosh, Saurabh Lodha

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69 Citations (Scopus)


Pn heterojunctions comprising layered van der Waals (vdW) semiconductors have been used to demonstrate current-rectifiers, photodetectors, and photovoltaic devices. However, a direct or near-direct heterointerface bandgap for enhanced photogeneration in high light-absorbing few-layer vdW materials remains unexplored. In this work, for the first time, density functional theory calculations show that the heterointerface of few-layer group-6 transition metal dichalcogenide (TMD) WSe2 with group-7 ReS2 results in a sizable (0.7 eV) near-direct type-II bandgap. The interlayer IR bandgap is confirmed through IR photodetection, and microphotoluminescence measurements demonstrate type-II alignment. Few-layer flakes exhibit ultrafast response time (5 μs), high responsivity (3 A/W), and large photocurrent-generation and responsivity-enhancement at the hetero-overlap region (10-100×). Large open-circuit voltage of 0.64 V and short-circuit current of 2.6 μA enable high output electrical power. Finally, long-term air-stability and facile single contact metal fabrication process make the multifunctional few-layer WSe2/ReS2 heterostructure diode technologically promising for next-generation optoelectronics.

Original languageEnglish
Pages (from-to)1707-1717
Number of pages11
JournalNano Letters
Issue number3
Publication statusPublished - 11 Mar 2020


  • infrared photodetection
  • interlayer bandgap
  • near-direct bandgap
  • pn heterojunction
  • ultrafast photodetection
  • van der Waals heterostructure

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