Improved Photoluminescence Efficiency of 2-D Semiconductors

Light emission from a single crystal monolayer of tungsten diselenide flake on a gold substrate. Part of the triangular flake rests on the patterned region of the substrate consisting of sub-20 nm wide trenches (Source: Wee / NUS)

Light emission from a single crystal mono­layer of tungsten dise­lenide flake on a gold substrate. Part of the triangular flake rests on the patterned region of the substrate consisting of sub-20 nm wide trenches (Source: Wee / NUS)

A team led by researchers from the National University of Singapore NUS has developed a method to enhance the photo­luminescence efficiency of tungsten diselenide, a two-dimensional semiconductor, paving the way for the appli­cation of such semi­conductors in advanced opto­electronic and photonic devices.

Tungsten diselenide is a single-molecule-thick semic­onductor that is part of an emerging class of materials called transition metal dichal­cogenides (TMDCs), which have the ability to convert light to electricity and vice versa, making them strong potential candidates for opto­electronic devices such as thin film solar cells, photo­detectors flexible logic circuits and sensors. However, its atomically thin structure reduces its absorption and photo­luminescence properties, thereby limiting its practical appli­cations.

By incor­porating monolayers of tungsten dise­lenide onto gold substrates with nanosized trenches, the research team, led by Andrew Wee of the Department of Physics at the NUS Faculty of Science, success­fully enhanced the nanomaterial’s photo­luminescence by up to 20,000-fold. This technological breakthrough creates new oppor­tunities of applying tungsten diselenide as a novel semi­conductor material for advanced appli­cations.

Wang Zhuo, a PhD candidate from the NUS Graduate School for Integrative Sciences and Engineering (NGS), explained, “This is the first work to demonstrate the use of gold plasmonic nano­structures to improve the photo­luminescence of tungsten diselenide, and we have managed to achieve an unpre­cedented enhance­ment of the light absorption and emission efficiency of this nano­material.” Elabora­ting on the signi­ficance of the novel method, Wee said, “The key to this work is the design of the gold plasmonic nanoarray templates. In our system, the resonances can be tuned to be matched with the pump laser wavelength by varying the pitch of the structures. This is critical for plasmon coupling with light to achieve optimal field confinement.”

The novel method developed by the NUS team, in colla­boration with researchers from the Singa­pore Univer­sity of Techno­logy and Design and Imperial College, opens up a new platform for inves­tigating novel electrical and optical properties in the hybrid system of gold with tungsten diselenide. Moving forward, the research team will further investigate the effective­ness of the lateral gold plasmon in enhancing the second harmonic genera­tion and electro­luminescence of TMDCs. They will also inves­tigate these effects in other two dimen­sional tran­sition metal dichal­cogenides with different band gaps, as they are expected to show different inter­action mechanisms. (Source: NUS)

Reference: Z. Wang et al.: Giant photoluminescence enhancement in tungsten-diselenide–gold plasmonic hybrid structures, Nat. Comm. 7, 11283; DOI: 10.1038/ncomms11283

Link: Centre for Advanced 2D Materials (T. S. Wee), University of Singapore NUS, Singapore

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