High-temperature driven inter-valley carrier transfer and significant fluorescence enhancement in multilayer WS<sub>2</sub>

Chen, Heyu; Li, Yuanzheng; Liu, Weizhen; Xu, Hongyan; Yang, Guochun; Shi, Jia; Feng, Qiushi; Tong, Ying; Liu, Xinfeng; Liu, Yichun

doi:10.1039/c8nh00123e

Cited by 13 publications

(13 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In addition to the multilayer WSe 2 system, we have confirmed that the model of thermally driven carrier redistribution is also applicable to the multilayer MoS 2 and multilayer WS 2 materials described in our previous studies . Similarly, the PL intensity increases by several times, even hundreds of times, at high temperatures compared to that achieved at room temperature.…”

supporting

confidence: 86%

“…Thus, heat engineering cannot only fulfill the modulation of the peak position but can also effectively transform the recombination channels of the indirect transition in multilayer WSe 2 . This phenomenon is different from other TMDs materials, which have fixed indirect transition pathways regardless of the changing temperature . This can be attributed to the transformation of an indirect bandgap from Λ–Γ to K–Γ as the temperature increases.…”

contrasting

confidence: 58%

“…Here, we have proposed an assumption for the enhanced K–K emission, and this assumption proposes that photogenerated carriers could gain extra energy from the ambient environment to achieve redistribution from an indirect bandgap to a direct bandgap in k ‐space via intervalley transfer . Figure d demonstrates the detailed physical processes regarding thermodriven intervalley transfer.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Unveiling Bandgap Evolution and Carrier Redistribution in Multilayer WSe₂: Enhanced Photon Emission via Heat Engineering

Liu

et al. 2019

Advanced Optical Materials

Self Cite

View full text Add to dashboard Cite

Semiconductor materials and relevant device technologies are important cornerstones for the rapid development of modern society. From the first generation of silicon and germanium semiconductors to the current third generation of silicon carbide and gallium nitride semiconductors, the applications of semiconductors have been widely expanded from initially integrated circuits and optical communications to advanced optoelectronic devices that are suitable for harsh working conditions (e.g., high temperature, high frequency, large power loading, and short wavelength emissions). [1,2] However, only the functionalities and performances of these traditional semiconductor materials have evolved; a breakthrough in reducing their dimensions and sizes has not yet been achieved. Obviously, such an evolution cannot push the boundaries of the stringent requirements of integrating electronic/optoelectronic components due to the quantum tunneling effect. Until 2004, the emergence of graphene has ushered in a new era of low-dimensional materials and technological innovations of high integration electronics and optoelectronics, [3,4] and has opened the door for 2D materials. Because graphene lacks an effective bandgap, recently, layered transition-metal dichalcogenides (TMDs) with optical bandgaps ranging from the visible to near-infrared spectral regions, [5][6][7][8] have been considered as a more promising candidate than graphene for 2D optoelectronic devices and digital electronic applications, [9][10][11][12][13] owing to their intriguing optical and electrical properties. [14][15][16][17][18] Monolayer TMDs with atomically thin thicknesses are direct bandgap semiconductors that possess superior lightemission characteristics. [15,19,20] However, the low optical density of states (DOS) and weak capacity for light absorption of these monolayer TMDs, [21,22] is limited by their ultrathin structure, which restricts their practical applications in the future. Compared to their monolayer counterparts, multilayer TMDs with an optically inactive indirect bandgap have a larger density of states and exhibit stronger photon absorption. Obviously, achieving the transformation of a bandgap structure from indirect bandgap to direct bandgap or propelling carriers in indirect bandgap to transform to direct bandgap in k-space Manipulating the bandgap structure and carrier distribution of multilayer transition metal dichalcogenides (TMDs) is crucial for improving their fluorescence efficiency and extending their optoelectronic applications. Herein, the evolution of the conduction band minimum of multilayer WSe 2 as a function of the temperature and thickness is experimentally demonstrated and an ≈70-fold fluorescence enhancement of the K-K direct emission is observed at 560 K in multilayer WSe 2 flakes (≈170 nm) by heat engineering. This abnormal enhancement is attributed to thermally driven carrier redistribution achieved via intervalley transfer, which is confirmed by the theoretical calculations and temperature-dependent time-resolved phot...

show abstract

supporting

confidence: 86%

contrasting

confidence: 58%

mentioning

confidence: 99%

See 1 more Smart Citation

Unveiling Bandgap Evolution and Carrier Redistribution in Multilayer WSe₂: Enhanced Photon Emission via Heat Engineering

Liu

et al. 2019

Advanced Optical Materials

Self Cite

View full text Add to dashboard Cite

show abstract

“…Compared to their monolayer counterparts, few-layer TMDs have many notable superiorities such as higher electron mobility, stronger photon absorption ability and larger optical density of states. 47 For example, the few-layer WS 2 has been demonstrated to be an excellent channel material with good electron mobilities of 234 cm 2 V −1 s −1 and on/off ratios exceeding 10 8 for the making of high performance field-effect transistors, required for both energy saving and high power electronics applications. 48 In this present work, we report the use of femtosecond transient absorption spectroscopy to address separately the ultrafast nonequilibrium dynamics of electrons and holes in the formation process of the lowest X A at the K-valley in few-layer WS 2 , used as an example.…”

Section: Introductionmentioning

confidence: 99%

Ultrafast nonequilibrium dynamic process of separate electrons and holes during exciton formation in few-layer tungsten disulfide

Chen

Guo

Lin

et al. 2021

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

show abstract

“…Recent progress has explored important physics related to the transition of excitons and trions, such as the valley lifetime of excitons (trions), spatial motion of excitons (trions), and spin and valley polarization dynamics of excitons (trions) . When excitons or trions transit from excited states to the ground state, excess energy will be dissipated by releasing photons in a process called fluorescence luminescence . The fluorescence lifetime is another parameter that describes the average time consumed during the excitons’ transition, playing a significant role in characterizing the exciton dynamics.…”

mentioning

confidence: 99%

Reduced Binding Energy and Layer-Dependent Exciton Dynamics in Monolayer and Multilayer WS₂

Liu

Wang

et al. 2019

ACS Nano

View full text Add to dashboard Cite

The exciton dynamics in WS2 from monolayer to four-layer was investigated by using fluorescence lifetime imaging measurement (FLIM). The transition process of negatively charged trions is measured and detected using a fluorescence detection method. Compared with neutral excitons, negatively charged trions have a longer fluorescence lifetime. Further exploration illustrated that the fluorescence lifetime of both neutral excitons and trions get longer when the thickness increased. When WS2 was added from monolayer to four-layer, lifetimes of direct transition excitons and trions tended to increase over 10 and 2.5 times, separately, whereas the lifetime of indirect transition excitons tended to be reduced by nearly 2.5 times. This layer-dependent signature is ascribed to the reduced binding energy in thicker WS2 at room temperature, which is verified by density theory functional calculation. Although the direct transition exciton dominates the whole fluorescence decay process, it is influenced by trions and dark excitons. Based on the FLIM results, we proposed four main exciton transition channels during the fluorescence luminescence process. Such layer-dependent transition channel conception helps to control the fluorescence lifetime, which determines the efficiency of the carriers’ separation.

show abstract

High-temperature driven inter-valley carrier transfer and significant fluorescence enhancement in multilayer WS₂

Abstract: A high-temperature driven carrier transfer process of multilayer WS2 is proposed and demonstrated for significant fluorescence emission enhancement.

Cited by 13 publications

References 38 publications

Unveiling Bandgap Evolution and Carrier Redistribution in Multilayer WSe₂: Enhanced Photon Emission via Heat Engineering

Unveiling Bandgap Evolution and Carrier Redistribution in Multilayer WSe₂: Enhanced Photon Emission via Heat Engineering

Ultrafast nonequilibrium dynamic process of separate electrons and holes during exciton formation in few-layer tungsten disulfide

Reduced Binding Energy and Layer-Dependent Exciton Dynamics in Monolayer and Multilayer WS₂

Contact Info

Product

Resources

About

High-temperature driven inter-valley carrier transfer and significant fluorescence enhancement in multilayer WS2

Abstract: A high-temperature driven carrier transfer process of multilayer WS2 is proposed and demonstrated for significant fluorescence emission enhancement.

Cited by 13 publications

References 38 publications

Unveiling Bandgap Evolution and Carrier Redistribution in Multilayer WSe2: Enhanced Photon Emission via Heat Engineering

Unveiling Bandgap Evolution and Carrier Redistribution in Multilayer WSe2: Enhanced Photon Emission via Heat Engineering

Ultrafast nonequilibrium dynamic process of separate electrons and holes during exciton formation in few-layer tungsten disulfide

Reduced Binding Energy and Layer-Dependent Exciton Dynamics in Monolayer and Multilayer WS2

Contact Info

Product

Resources

About

High-temperature driven inter-valley carrier transfer and significant fluorescence enhancement in multilayer WS₂

Unveiling Bandgap Evolution and Carrier Redistribution in Multilayer WSe₂: Enhanced Photon Emission via Heat Engineering

Unveiling Bandgap Evolution and Carrier Redistribution in Multilayer WSe₂: Enhanced Photon Emission via Heat Engineering

Reduced Binding Energy and Layer-Dependent Exciton Dynamics in Monolayer and Multilayer WS₂