Transition metal dichalcogenides (TMDCs) represent a novel and sustainable material basis for ultrathin optoelectronic devices. Although various approaches toward light-emitting devices, e.g., based on exfoliated or chemical vapor deposited (CVD) TMDC monolayers, have been reported, they all suffer from limited scalability and reproducibility required for industrial fabrication. Here, we demonstrate a light-emitting device in a scalable approach by embedding metal−organic (MO-)­CVD WS2 monolayers into a vertical p–i–n device architecture using organic and inorganic injection layers. Red electroluminescence is emitted from an active area of 6 mm2 starting already at a driving voltage of about 2.5 V.

transition metal dichalcogenides (TMDCs) are seen as promising candidates for flexible electronic and optoelectronic devices due to their high tensile strength and favorable optical properties. Molybdenum disulfide (MoS 2 ) is a benchmark material for TMDCs, which has already been studied extensively. Here, we report on highly responsive flexible few-layer MoS 2 photodetectors based on MoS 2 synthesized uniformly for full coverage of 2 in. sapphire wafers using metalorganic vapor-phase epitaxy (MOVPE). Device performance is studied by electro-optical characterization. Electrostatic gating allows tuning both the responsivity between 150 and 920 A/W and the specific detectivity between almost 10 12 and 10 10 Jones. The measured spectrally resolved responsivities of the detectors suggest applications in the blue-light range, with opportunities for fine-tuning the most sensitive wavelength through gating, as shown through optical simulations. Finally, the flexible devices were bent to demonstrate their suitability for flexible electronics in fields of future Internet of Things and medical devices.

Using mechanically flexible substrates for complex (opto-)electronic device architectures is of growing interest in the area of consumer electronics, [1] for wearables [2] or for applications in biology and life science. [3] Potential candidates for light-emitting devices (LEDs) on curved or flexible surfaces are organic LEDs (OLEDs) [4] or quantum dot LEDs [5,6] (QD-LEDs). Higher durability is achieved by bottom-up approaches, which combine individual inorganic micro-LEDs to flexible arrays. [1,3] Although two-dimensional (2D) materials are ideally suited for flexible device applications, [7-9] only a few flexible prototype devices such as transistors [10-12] or photodetectors [13-15] have

Metal-free chemical vapor deposition (CVD) of single-layer graphene (SLG) on c-plane sapphire has recently been demonstrated for wafer diameters of up to 300 mm, and the high quality of the SLG layers is generally characterized by integral methods. By applying a comprehensive analysis approach, distinct interactions at the graphene-sapphire interface and local variations caused by the substrate topography are revealed. Regions near the sapphire step edges show tiny wrinkles with a height of about 0.2 nm, framed by delaminated graphene as identified by the typical Dirac cone of free graphene. In contrast, adsorption of CVD SLG on the hydroxyl-terminated α-Al2O3 (0001) terraces results in a superstructure with a periodicity of (2.66 ± 0.03) nm. Weak hydrogen bonds formed between the hydroxylated sapphire surface and the π-electron system of SLG result in a clean interface. The charge injection induces a band gap in the adsorbed graphene layer of about (73 ± 3) meV at the Dirac point. The good agreement with the predictions of a theoretical analysis underlines the potential of this hybrid system for emerging electronic applications.

Fabrication of transition metal dichalcogenides (TMDCs) via metalorganic chemical vapor deposition (MOCVD) represents one of the most attractive routes to large-scale 2D material layers. Although good homogeneity and electrical conductance have been reported recently, the relation between growth parameters and photoluminescence (PL) intensity-one of the most important parameters for optoelectronic applications-has not yet been discussed for MOCVD TMDCs. In this work, MoS is grown via MOCVD on sapphire (0001) substrates using molybdenum hexacarbonyl (Mo(CO), MCO) and di-tert-butyl sulphide as precursor materials. A prebake step under H atmosphere combined with a reduced MCO precursor flow increases the crystal grain size by one order of magnitude and strongly enhances PL intensity with a clear correlation to the grain size. A decrease of the linewidth of both Raman resonances and PL spectra down to full width at half maxima of 3.2 cm for the E Raman mode and 60 meV for the overall PL spectrum indicate a reduced defect density at optimized growth conditions.