Synthetic WSe
            <sub>2</sub>
            monolayers with high photoluminescence quantum yield

Kim, Hyungjin; Ahn, Geun Ho; Cho, Joy; Amani, Matin; Mastandrea, James P.; Groschner, Catherine; Lien, Der Hsien; Zhao, Yingbo; Ager, Joel W.; Scott, Mary; Chrzan, D. C.; Javey, Ali

doi:10.1126/sciadv.aau4728

Cited by 97 publications

(87 citation statements)

References 41 publications

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“…The strain should not be the main factor causing the distribution of PL intensity due to the following reasons. First, for WSe 2 grown at 900 °C, the center and the edge regions undergo the same heat treatment; the resulted strain level should be the same [59]. Secondly, Kim et al compared the PL of WS 2 before and after transferring to transmission electron microscopy (TEM) copper grid, excluding the possibility of the substrate caused nonuniform PL and Raman distribution [58].…”

Section: Resultsmentioning

confidence: 99%

Quick Optical Identification of the Defect Formation in Monolayer WSe2 for Growth Optimization

et al. 2019

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Bottom-up epitaxy has been widely applied for transition metal dichalcogenides (TMDCs) growth. However, this method usually leads to a high density of defects in the crystal, which limits its optoelectronic performance. Here, we show the effect of growth temperature on the defect formation, optical performance, and crystal stability in monolayer WSe 2 via a combination of Raman and photoluminescence (PL) spectroscopy study. We found that the defect formation and distribution in monolayer WSe 2 are closely related to the growth temperature. These defect density and distribution can be controlled by adjusting the growth temperature. Aging experiments directly demonstrate that these defects are an active center for the decomposition process. Instead, monolayer WSe 2 grown under optimal conditions shows a strong and uniform emission dominated by neutral exciton at room temperature. The results provide an effective approach to optimize TMDCs growth. Electronic supplementary material The online version of this article (10.1186/s11671-019-3110-z) contains supplementary material, which is available to authorized users.

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Section: Resultsmentioning

confidence: 99%

Quick Optical Identification of the Defect Formation in Monolayer WSe2 for Growth Optimization

et al. 2019

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“…Therefore, non‐precious catalysts, such as MoS 2 and other transition metal dichalcogenides (TMDCs) that drive HER at relatively low overpotentials, have been reported as promising electrocatalysts due to their layered structure, unique electronic configuration and electrochemical stability. Following the successful implementation of transition metal sulfides in various applications, transition metal selenides are now the rising stars; heavier chalcogens provide better electrical conductivity, which is very important for faster reaction kinetics of the HER electrocatalysis, as well for energy storage, optoelectronic and magnetic applications …”

Section: Introductionmentioning

confidence: 99%

Co‐Doped MoSe₂ Nanoflowers as Efficient Catalysts for Electrochemical Hydrogen Evolution Reaction (HER) in Acidic and Alkaline Media

Zimron

Zilberman

Kadam

et al. 2020

Israel Journal of Chemistry

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Transition metal dichalcogenides (TMDCs) based materials are considered as highly active alternatives to the precious Pt‐based catalysts for the hydrogen evolution reaction (HER). In particular, MoSe2 emerges as a promising catalyst due to its abundance and electrochemical stability, but further modifications are still required to enhance its performance, specifically in alkaline conditions. Here, we developed a method to obtain MoSe2 with two cobalt doping patterns: homogeneously doped and edge doped nanoflowers, with abundant edge sites and extended surface area. The results show that low concentration of doping enhances the catalytic activity toward HER. Incorporation of cobalt as a substituent dopant within the layered structure of MoSe2 appears to have two major contributions: it changes the chemical environment providing more active sites with favored hydrogen adsorption properties, and improves the charge transfer resistance and thus facilitates the HER kinetics. Moreover, the homogeneous and edge‐doped nanoflowers show different pH‐dependence of HER activity. Edge‐doped samples exhibit significantly improved performance in acidic medium, while the overpotential increases in alkaline environment upon doping. A mechanistic explanation of the observed effect is proposed. This work opens up an additional path for improving the catalytic activity of TMDCs in acidic or alkaline medium using a simple and facile method with only small quantities of dopants.

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“…For the case of exfoliated WS 2 , a droop is observed at the high pump‐power regime, which is attributed to biexcitonic recombination . The absence of this behavior has been previously observed in CVD‐grown WSe 2 and MoS 2 ; however, the underlying mechanism is unknown, although it could be due to differences in background doping or the presence of strain as a result of the growth process . Importantly, the lack of droop in the PL QY of CVD WS 2 at high injection levels makes the material a highly attractive candidate for an electroluminescent device.…”

Section: Resultsmentioning

confidence: 86%

Centimeter‐Scale and Visible Wavelength Monolayer Light‐Emitting Devices

Cho

Amani

Lien

et al. 2019

Adv Funct Materials

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Monolayer 2D transition metal dichalcogenides (TMDCs) have shown great promise for optoelectronic applications due to their direct bandgaps and unique physical properties. In particular, they can possess photoluminescence quantum yields (PL QY) approaching unity at the ultimate thickness limit, making their application in light-emitting devices highly promising. Here, large-area WS 2 grown via chemical vapor deposition is synthesized and characterized for visible (red) light-emitting devices. Detail optical characterization of the synthesized films is performed, which show peak PL QY as high as 12%. Electrically pumped emission from the synthetic WS 2 is achieved utilizing a transient-mode electroluminescence device structure, which consists of a single metal-semiconductor contact and alternating gate fields to achieve bipolar emission. Utilizing this aforementioned structure, a centimeter-scale (≈0.5 cm 2 ) visible (640 nm) display is demonstrated, fabricated using TMDCs to showcase the potential of this material system for display applications.absorbed, and is a key figure of merit as it directly dictates the final efficiency when the materials are made into light-emitting devices or photovoltaics. Various microscale light-emitting devices have been demonstrated using TMDCs. [13][14][15][16] However, a challenge has been the requirement for simultaneous formation of low-resistance contacts to both electrons and holes in the same device. In one specific architecture, we recently demonstrated efficient bipolar carrier injection using transientmode operation through a single Schottky contact. [17] The device effectively acts as a light-emitting capacitor, with minimal dependence on the contact metal to the semiconductor. This device structure was shown to work with exfoliated monolayers of MoS 2 , WS 2 , MoSe 2 , and WSe 2 . Furthermore, large-area (3 mm × 2 mm) emission was demonstrated using WSe 2 monolayers grown by chemical vapor deposition (CVD). Although the WSe 2 devices were bright, their emission is in the near-infrared regime (750 nm peak emission). Recently, millimeter-scale WS 2 devices operated in the visible wavelength regime were demonstrated using a vertical architecture with quantum dots and polymers as electron/hole injection layers, but a more efficient device is still demanded. [18] In this regard, we report a centimeter-scale, bright, visible light-emitting device based on WS 2 monolayers synthesized via CVD [19][20][21] using a simple capacitor structure. The CVD-synthesized material exhibits a respectable peak PL QY of approximately 10%, without a droop at high injection levels. Using this material, we fabricate a transient-electroluminescence (t-EL) device and characterize its performance; in particular, its efficient light emission at high injection levels. Finally, we also fabricate a sixteen-pixel display with bright red EL emission (640 nm, peak output power 14 µW cm −2 ), which is visible in ambient room lighting. Figure 1a shows the PL spectra of the synthesized WS 2 measured over a p...

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Synthetic WSe ₂ monolayers with high photoluminescence quantum yield

Abstract: A simple substrate decoupling method with optimized growth conditions enables a high-quality synthetic monolayer semiconductor.

Cited by 97 publications

References 41 publications

Quick Optical Identification of the Defect Formation in Monolayer WSe2 for Growth Optimization

Quick Optical Identification of the Defect Formation in Monolayer WSe2 for Growth Optimization

Co‐Doped MoSe₂ Nanoflowers as Efficient Catalysts for Electrochemical Hydrogen Evolution Reaction (HER) in Acidic and Alkaline Media

Centimeter‐Scale and Visible Wavelength Monolayer Light‐Emitting Devices

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Synthetic WSe 2 monolayers with high photoluminescence quantum yield

Abstract: A simple substrate decoupling method with optimized growth conditions enables a high-quality synthetic monolayer semiconductor.

Cited by 97 publications

References 41 publications

Quick Optical Identification of the Defect Formation in Monolayer WSe2 for Growth Optimization

Quick Optical Identification of the Defect Formation in Monolayer WSe2 for Growth Optimization

Co‐Doped MoSe2 Nanoflowers as Efficient Catalysts for Electrochemical Hydrogen Evolution Reaction (HER) in Acidic and Alkaline Media

Centimeter‐Scale and Visible Wavelength Monolayer Light‐Emitting Devices

Contact Info

Product

Resources

About

Synthetic WSe ₂ monolayers with high photoluminescence quantum yield

Co‐Doped MoSe₂ Nanoflowers as Efficient Catalysts for Electrochemical Hydrogen Evolution Reaction (HER) in Acidic and Alkaline Media