2/18/2024 0 Comments Spectra twoCharge-transfer excitons at organic semiconductor surfaces and interfaces. Exciton dynamics in suspended monolayer and few-layer MoS2 2D crystals. Measurement of the optical conductivity of graphene. Gate-variable optical transitions in graphene. New first order Raman-active modes in few layered transition metal dichalcogenides. Effects of lower symmetry and dimensionality on Raman spectra in two-dimensional WSe2. Identification of individual and few layers of WS2 using Raman spectroscopy. Anomalous lattice vibrations of single-and few-layer MoS2. Controlled growth of high-quality monolayer WS2 layers on sapphire and imaging its grain boundary. Grains and grain boundaries in highly crystalline monolayer molybdenum disulphide. Ultrafast long-range charge separation in organic semiconductor photovoltaic diodes. Coherence and uncertainty in nanostructured organic photovoltaics. Hot charge-transfer excitons set the time limit for charge separation at donor/acceptor interfaces in organic photovoltaics. Hot exciton dissociation in polymer solar cells. Optical spectrum of MoS2: many-body effects and diversity of exciton states. Theory of neutral and charged excitons in monolayer transition metal dichalcogenides. Emerging photoluminescence in monolayer MoS2. Atomically thin MoS2: a new direct-gap semiconductor. Electronic properties of the MoS2-WS2 heterojunction. Novel hetero-layered materials with tunable direct band gaps by sandwiching different metal disulfides and diselenides. Band offsets and heterostructures of two-dimensional semiconductors. Electronic structures and optical properties of realistic transition metal dichalcogenide heterostructures from first principles. Band alignment of two-dimensional transition metal dichalcogenides: application in tunnel field effect transistors. Ultrasensitive photodetectors based on monolayer MoS2. Lopez-Sanchez, O., Lembke, D., Kayci, M., Radenovic, A. Spin–layer locking effects in optical orientation of exciton spin in bilayer WSe2. Controlled charge trapping by molybdenum disulphide and graphene in ultrathin heterostructured memory devices. Field-effect tunneling transistor based on vertical graphene heterostructures. Hofstadter's butterfly and the fractal quantum Hall effect in moiré superlattices. Massive Dirac fermions and Hofstadter butterfly in a van der Waals heterostructure. Cloning of Dirac fermions in graphene superlattices. Emergence of superlattice Dirac points in graphene on hexagonal boron nitride. Highly efficient gate-tunable photocurrent generation in vertical heterostructures of layered materials. Strong light–matter interactions in heterostructures of atomically thin films. Such ultrafast charge transfer in van der Waals heterostructures can enable novel two-dimensional devices for optoelectronics and light harvesting. We show that hole transfer from the MoS 2 layer to the WS 2 layer takes place within 50 fs after optical excitation, a remarkable rate for van der Waals coupled two-dimensional layers. Here, we report the first experimental observation of ultrafast charge transfer in photoexcited MoS 2/WS 2 heterostructures using both photoluminescence mapping and femtosecond pump–probe spectroscopy. Theory predicts that many stacked MX 2 heterostructures form type II semiconductor heterojunctions that facilitate efficient electron–hole separation for light detection and harvesting 12, 13, 14, 15, 16. MX 2 heterostructures are particularly exciting for novel optoelectronic and photovoltaic applications, because two-dimensional MX 2 monolayers can have an optical bandgap in the near-infrared to visible spectral range and exhibit extremely strong light–matter interactions 2, 3, 11. Van der Waals heterostructures have recently emerged as a new class of materials, where quantum coupling between stacked atomically thin two-dimensional layers, including graphene, hexagonal-boron nitride and transition-metal dichalcogenides (MX 2), give rise to fascinating new phenomena 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.
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