Molybdenum disulfide (MoS2) and tungsten disulfide (WS2), two representative transition metal dichalcogenide materials, have captured tremendous interest for their unique electronic, optical, and chemical properties. Compared with MoS2 and WS2, molybdenum ditelluride (MoTe2) and tungsten ditelluride (WTe2) possess similar lattice structures while having smaller bandgaps (less than 1 eV), which is particularly interesting for applications in the near‐infrared wavelength regime. Here, few‐layer MoTe2/WTe2 nanosheets are fabricated by a liquid exfoliation method using sodium deoxycholate bile salt as surfactant, and the nonlinear optical properties of the nanosheets are investigated. The results demonstrate that MoTe2/WTe2 nanosheets exhibit nonlinear saturable absorption property at 1.55 μm. Soliton mode‐locking operations are realized separately in erbium‐doped fiber lasers utilizing two types of MoTe2/WTe2‐based saturable absorbers, one of which is prepared by depositing the nanosheets on side polished fibers, while the other is fabricated by mixing the nanosheets with polyvinyl alcohol and then evaporating them on substrates. Numerous applications may benefit from the nonlinear saturable absorption features of MoTe2/WTe2 nanosheets, such as visible/near‐infrared pulsed laser, materials processing, optical sensors, and modulators.

Optoelectronic applications require materials both responsive to objective photons and able to transfer carriers, so new two‐dimensional (2D) semiconductors with appropriate band gaps and high mobilities are highly desired. A broad range of band gaps and high mobilities of a 2D semiconductor family, composed of monolayer of Group 15 elements (phosphorene, arsenene, antimonene, bismuthene) is presented. The calculated binding energies and phonon band dispersions of 2D Group 15 allotropes exhibit thermodynamic stability. The energy band gaps of 2D semiconducting Group 15 monolayers cover a wide range from 0.36 to 2.62 eV, which are crucial for broadband photoresponse. Significantly, phosphorene, arsenene, and bismuthene possess carrier mobilities as high as several thousand cm2 V−1 s−1. Combining such broad band gaps and superior carrier mobilities, 2D Group 15 monolayers are promising candidates for nanoelectronics and optoelectronics.

Understanding the growth behavior of nanocrystals (NCs), especially when heteroatoms are introduced, is very important for the optimization of doping (or alloying) and optoelectronic performances. Here, it is reported on the observation of alloying‐facilitated self‐assembly of MgZnO NCs and the underlying mechanism of alloying concentration‐dependent surface grafting. Using the developed one‐pot thermolysis of Zn and Mg organic salts with the help of oleylamine (OAm) and oleic acid (OA), the Mg ions can be introduced into the ZnO lattice without phase separation with concentrations as high as 20%. Interestingly, with the increase of Mg alloying concentration, the morphologies of the products transform from monodispersed NCs to nanoflowers, and then nanobouquet superstructures, which have quasi‐monocrystal features and obey the oriented attachment rules. According to the analyses of surface functional groups, a mechanism involving concentration‐dependent surface grafting is proposed for such alloying‐facilitated self‐assembly.

Novel quantum‐dot light‐emitting diodes based on all‐inorganic perovskite CsPbX3 (X = Cl, Br, I) nanocrystals are reported. The well‐dispersed, single‐crystal quantum dots (QDs) exhibit high quantum yields, and tunable light emission wavelength. The demonstration of these novel perovskite QDs opens a new avenue toward designing optoelectronic devices, such as displays, photodetectors, solar cells, and lasers.

As new members of carbon material family, carbon and graphene quantum dots (CDs, GQDs) have attracted tremendous attentions for their potentials for biological, optoelectronic, and energy related applications. Among these applications, bio‐imaging has been intensively studied, but optoelectronic and energy devices are rapidly rising. In this Feature Article, recent exciting progresses on CD‐ and GQD‐based optoelectronic and energy devices, such as light emitting diodes (LEDs), solar cells (SCs), photodetctors (PDs), photocatalysis, batteries, and supercapacitors are highlighted. The recent understanding on their microstructure and optical properties are briefly introduced in the first part. Some important progresses on optoelectronic and energy devices are then addressed as the main part of this Feature Article. Finally, a brief outlook is given, pointing out that CDs and GQDs could play more important roles in communication‐ and energy‐functional devices in the near future.