Graphene has attracted large interest in photonic applications owing to its promising optical properties, especially its ability to absorb light over a broad wavelength range, which has lead to several studies on pure monolayer graphene-based photodetectors. However, the maximum responsivity of these photodetectors is below 10 mA W À 1 , which significantly limits their potential for applications. Here we report high photoresponsivity (with high photoconductive gain) of 8.61 A W À 1 in pure monolayer graphene photodetectors, about three orders of magnitude higher than those reported in the literature, by introducing electron trapping centres and by creating a bandgap in graphene through band structure engineering. In addition, broadband photoresponse with high photoresponsivity from the visible to the mid-infrared is experimentally demonstrated. To the best of our knowledge, this work demonstrates the broadest photoresponse with high photoresponsivity from pure monolayer graphene photodetectors, proving the potential of graphene as a promising material for efficient optoelectronic devices.

Atom-thin transition metal dichalcogenides (TMDs) have emerged as fascinating materials and key structures for electrocatalysis. So far, their edges, dopant heteroatoms and defects have been intensively explored as active sites for the hydrogen evolution reaction (HER) to split water. However, grain boundaries (GBs), a key type of defects in TMDs, have been overlooked due to their low density and large structural variations. Here, we demonstrate the synthesis of wafer-size atom-thin TMD films with an ultra-high-density of GBs, up to ~1012 cm−2. We propose a climb and drive 0D/2D interaction to explain the underlying growth mechanism. The electrocatalytic activity of the nanograin film is comprehensively examined by micro-electrochemical measurements, showing an excellent hydrogen-evolution performance (onset potential: −25 mV and Tafel slope: 54 mV dec−1), thus indicating an intrinsically high activation of the TMD GBs.

Anisotropic 2D materials exhibit unique optical, electrical, and thermoelectric properties that open up possibilities for diverse angle‐dependent devices. However, the explored anisotropic 2D materials are very limited and the methods to identify the crystal orientations and to study the in‐plane anisotropy are in the initial stage. Here azimuth‐dependent reflectance difference microscopy (ADRDM), angle‐resolved Raman spectra, and electrical transport measurements are used to systematically characterize the influence of the anisotropic structure on in‐plane optical and electrical anisotropy of 2D GeAs, a novel group IV–V semiconductor. It is proved that ADRDM offers a way to quickly identify the crystal orientations and also to directly characterize the in‐plane optical anisotropy of layered GeAs. The anisotropic electrical transport behavior of few‐layer GeAs field‐effect transistors is further measured and the anisotropic ratio of the mobility is as high as 4.6, which is higher than the other 2D anisotropic materials such as black phosphorus. The dependence of the Raman intensity anisotropy on the sample thickness, excitation wavelength, and polarization configuration is investigated both experimentally and theoretically. These data will be useful for designing new high‐performance devices and the results suggest a general methodology for characterizing the in‐plane anisotropy of low‐symmetry 2D materials.

In this review, we summarize the recent progress in the aspects of the fabrication methods for large-area perovskite films, improving the efficiency and stability of the large-area PSC devices.