Near-Direct Bandgap WSe<sub>2</sub>/ReS<sub>2</sub> Type-II pn Heterojunction for Enhanced Ultrafast Photodetection and High-Performance Photovoltaics.
basic_science · Level V
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- Record sourced from PubMed, PMID 32078333.
- Also identified by DOI 10.1021/acs.nanolett.9b04879.
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Abstract
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) WSe<sub>2</sub> with group-7 ReS<sub>2</sub> 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 WSe<sub>2</sub>/ReS<sub>2</sub> heterostructure diode technologically promising for next-generation optoelectronics.