2D semiconductors such as transition metal dichalcogenides (TMDs) and black phosphorus (BP) are currently attracting great attention due to their intrinsic bandgaps and strong excitonic emissions, making them potential candidates for novel optoelectronic applications. Optoelectronic devices fabricated from 2D semiconductors exhibit many-body complexes (exciton, trion, biexciton, etc.) which determine the materials optical and electrical properties. Characterization and manipulation of these complexes have become a reality due to their enhanced binding energies as a direct result from reduced dielectric screening and enhanced Coulomb interactions in the 2D regime. Furthermore, the atomic thickness and extremely large surface-to-volume ratio of 2D semiconductors allow the possibility of modulating their inherent optical, electrical, and optoelectronic properties using a variety of different environmental stimuli. To fully realize the potential functionalities of these many-body complexes in optoelectronics, a comprehensive understanding of their formation mechanism is essential. A topical and concise summary of the recent frontier research progress related to many-body complexes in 2D semiconductors is provided here. Moreover, detailed discussions covering the aspects of fundamental theory, experimental investigations, modulation of properties, and optoelectronic applications are given. Lastly, personal insights into the current challenges and future outlook of many-body complexes in 2D semiconducting materials are presented.

A review on performance enhancement techniques for ambient vibration energy A review on performance enhancement techniques for ambient vibration energy harvesters harvesters

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The realization of ordered strain fields in 2D crystals is an intriguing perspective in many respects, including the instauration of novel transport regimes and enhanced device performances. However, the current straining techniques hardly allow to reach strains higher than ≈3% and in most cases there is no control over the strain distribution. In this work, a method is demonstrated to subject micrometric regions of atomically thin molybdenum disulfide (MoS2) to giant strains with the desired ordering. Selective hydrogen‐irradiation of bulk flakes allows the creation of arrays of size/position‐controlled monolayer domes containing pressurized hydrogen. However, the gas pressure is ruled by energy minimization, limiting the extent and geometry of the mechanical deformation of the 2D membrane. Here, a protocol is developed to create a mechanical constraint, that alters remarkably the morphology of the domes, otherwise subject to universal scaling laws, as demonstrated by atomic force microscopy. This enables the realization of unprecedented periodic configurations of large strain gradients—estimated by numerical simulations—with the highest strains being close to the rupture critical values (>10%). The creation of such high strains is confirmed by Raman experiments. The method proposed here represents an important step toward the strain engineering of 2D crystals.