Due to the intriguing anisotropic optical and electrical properties, low‐symmetry 2D materials are attracting a lot of interest both for fundamental studies and fabricating novel electronic and optoelectronic devices. Identifying new promising low‐symmetry 2D materials will be rewarding toward the evolution of nanoelectronics and nano‐optoelectronics. In this work, germanium diarsenide (GeAs2), a group IV–V semiconductor with novel low‐symmetry puckered structure, is introduced as a favorable highly anisotropic 2D material into the rapidly growing 2D family. The structural, vibrational, electrical, and optical in‐plane anisotropy of GeAs2 is systematically investigated both theoretically and experimentally, combined with thickness‐dependent studies. Polarization‐sensitive photodetectors based on few‐layer GeAs2 exhibit highly anisotropic photodetection behavior with lineally dichroic ratio up to ≈2. This work on GeAs2 will excite interests in the less exploited regime of group IV–V compounds.

Infrared detection at optical communication wavelength is of great significance because of their diverse commercial and military communication applications. The layered Bi2Se3 with a narrow band gap of 0.3 eV is regarded as a promising candidate toward high‐performance terahertz to infrared applications. However, the controllable synthesis of large‐size ultrathin Bi2Se3 flakes remains a challenge owing to complex nucleation process and infrared telecommunication photodetectors based on Bi2Se3 flakes are rarely reported. Here, large size (submillimeter: 0.2–0.4 mm in lateral dimensions) and ultrathin (thickness: 3 nm to few nanometers) 2D Bi2Se3 flakes with high crystal quality are obtained by suppressing the nucleation density. More importantly, back‐gate field‐effect transistor based on Bi2Se3 flake exhibits an ultrahigh on/off current ratio of 106 and competitive mobility of 39.4 cm2 V−1 s−1. Moreover, excellent on/off ratio of 972.5, responsivity of 23.8 A W−1, and external quantum efficiency of 2035% are obtained from Bi2Se3‐based photodetector at 1456 nm in the E‐band of the telecommunication range. With controlled morphology and excellent photoresponse performance, the Bi2Se3 photodetector shows great potential in the optoelectronic field including communications, military, and remote sensing.

Two-dimensional (2D) materials exhibit high sensitivity to structural defects due to the nature of interfacetype materials, and the corresponding structural defects can effectively modulate their inherent properties in turn, giving them a wide application range in high-performance and functional devices. 2D γ-Ga 2 S 3 is a defective semiconductor with outstanding optoelectronic properties. However, its controllable preparation has not been implemented yet, which hinders exploring its potential applications. In this work, we introduce nonlayered γ-Ga 2 S 3 into the 2D materials family, which was successfully synthesized via the space-confined chemical vapor deposition method. Its intriguing defective structure are revealed by high-resolution transmission electron microscopy and temperature-dependent cathodoluminescence spectra, which endow the γ-Ga 2 S 3 -based device with a broad photoresponse from the ultraviolet to near-infrared region and excellent photoelectric conversion capability. Simultaneously, the device also exhibits excellent ultraviolet detection ability (R λ = 61.3 A W −1 , I on /I off = 851, EQE = 2.17× 10 4 %, D* = 1.52× 10 10 Jones @350 nm), and relatively fast response (15 ms). This work provides a feasible way to fabricate ultrathin nonlayered materials and explore the potential applications of a 2D defective semiconductor in high-performance broadband photodetection, which also suggests a promising future of defect creation in optimizing photoelectric properties.

In the post‐Moore era, 2D materials with rich physical properties have attracted widespread attention from the scientific and industrial communities. Among 2D materials, the 2D homojunctions are of great promise in designing novel electronic and optoelectronic devices due to their unique geometries and properties such as homogeneous components, perfect lattice matching, and efficient charge transfer at the interface. In this article, a pioneering review focusing on the structural design and device application of 2D homojunctions such as p–n homojunctions, heterophase homojunctions, and layer‐engineered homojunctions is provided. The preparation strategies to construct 2D homojunctions including vapor‐phase deposition, lithium intercalation, laser irradiation, chemical doping, electrostatic doping, and photodoping are summarized in detail. Specifically, a careful review on the applications of the 2D homojunctions in electronics (e.g., field‐effect transistors, rectifiers, and inverters) and optoelectronics (e.g., light‐emitting diodes, photovoltaics, and photodetectors) is provided. Eventually, the current challenges and future perspectives are commented for promoting the rapid development of 2D homojunctions.

As an important member of group VA–VIA semiconductors, 2D Sb2Se3 has drawn widespread attention thanks to its outstanding optoelectronic properties as compared to the bulk material. However, due to the intrinsic chain‐like crystal structure, the controllable synthesis of ultrathin 2D planar Sb2Se3 nanostructures still remains a huge challenge. Herein, for the first time, the crystal structure limitation is overcome and the successful structural evolution of 2D ultrathin Sb2Se3 flakes (as thin as 1.3 nm), by introducing a sodium‐mediated chemical vapor deposition (CVD) growth method, is realized. The formation of 2D planar geometry is mainly attributed to the preferential growth of (010) plane with the lowest formation energy. The thickness‐dependent band structure of 2D Sb2Se3 flakes shows a wide absorption band from UV to NIR region (300–1000 nm), suggesting its potential application in broadband photodetection. Strikingly, the Sb2Se3 flakes–based photodetector demonstrates excellent performance such as broadband response varying from UV to NIR region, high responsivity of 4320 mA W−1, fast response time (τrise ≈ 13.16 ms and τdecay ≈ 9.61 ms), and strong anisotropic ratio of 2.5@ 532 nm, implying promising potential application in optoelectronics.