Nanoelectronics is in urgent demand of exceptional device architecture with ultrathin thickness below 10 nm and dangling‐bond‐free surface to break through current physical bottleneck and achieve new record of integration level. The advance in 2D van der Waals materials endows scientists with new accessibility. This study reports an all‐layered 2D Bi2Te3‐SnSe‐Bi2Te3 photodetector, and the broadband photoresponse of the device from ultraviolet (370 nm) to near‐infrared (808 nm) is demonstrated. In addition, the optimized responsivity reaches 5.5 A W−1, with the corresponding eternal quantum efficiency of 1833% and detectivity of 6 × 1010 cm Hz1/2 W−1. These figures‐of‐merits are among the best values of the reported all‐layered 2D photodetectors, which are several orders of magnitude higher than those of the previous SnSe photodetectors. The superior device performance is attributed to the synergy of highly conductive surface state of Bi2Te3 topological insulator, perfect band alignment between Bi2Te3 and SnSe as well as small interface potential fluctuation. Meanwhile, the all‐layered 2D device is further constructed onto flexible mica substrate and its photoresponse is maintained roughly unchanged upon 60 bending cycles. The findings represent a fundamental scenario for advancement of the next generation high performance and high integration level flexible optoelectronics.

Two‐dimensional‐material‐based self‐driven photodetectors show high sensitivity, fast and broadband response under built‐in electric field in a P–N junction configuration. However, the methods, including doping and multiple transfer processes, for constructing the heterostructures is complex and time‐costing. On the other hand, asymmetric Schottky barrier heights caused by metal electrodes scale, kinds, contact area and thickness can lead to zero‐bias driven photo‐response. In this work, a metal–semiconductor–metal irregular WS2 photodetector with symmetric electrodes are achieved by wet‐transfer. A high zero‐bias photo‐responsivity of 777 mA W−1, a fast response speed of 7.8/37.2 ms, a Ilight/Idark ratio of 104 and a high detectivity of 4.94 × 1011 Jones under 405 nm light are obtained because of a Schottky barrier height difference of ≈50.2 mV through Fermi‐level pinning effect and different contact area. The responsivity at −2 V is stable in the range of 2.23 to 3.45 A W−1 and the empirical factor reaches to 0.99 by the efficient carrier generation process. The WS2 asymmetric Schottky photodetectors outperform most heterostructure based photodiodes. This paper provides a facile route toward self‐powered photodetectors with high performance, easy processing and simple architecture for future applications.

Because of their great potential for academic investigation and practical application in next-generation optoelectronic devices, ternary layered semiconductors have attracted considerable attention in recent years. Similar to the applications of traditional layered materials, practical applications of ternary layered semiconductor alloys require the synthesis of large-area samples. Here, we report the preparation of centimeter-scale and high-quality MoWSe alloy films on both a rigid SiO/Si substrate and a flexible polyimide (PI) substrate. Then, photodetectors based on these alloy films are fabricated, which are capable of conducting broad-band photodetection from ultraviolet to near-infrared region (370-808 nm) with high performance. The photodetector on SiO/Si substrates demonstrates a high responsivity (R) of 77.1 A/W, an outstanding detectivity (D*) of 1.1 × 10 Jones, and a fast response time of 8.3 ms. These figures-of-merit are much superior to those of the counterparts of binary material-based devices. Moreover, the photodetector on PI substrates also achieves high performance (R = 63.5 A/W, D* = 3.56 × 10 Jones). And no apparent degradation in the device properties is observed even after 100 bending cycles. These results make MoWSe alloy a highly qualified candidate for next-generation optoelectronic applications.

We demonstrate a ytterbium (Yb) and an erbium (Er)-doped fiber laser Q-switched by a solution processed, optically uniform, few-layer tungsten disulfide saturable absorber (WS2-SA). Nonlinear optical absorption of the WS2-SA in the sub-bandgap region, attributed to the edge-induced states, is characterized by 3.1% and 4.9% modulation depths with 1.38 and 3.83 MW/cm2 saturation intensities at 1030 and 1558 nm, respectively. By integrating the optically uniform WS2-SA in the Yb- and Er-doped laser cavities, we obtain self-starting Q-switched pulses with microsecond duration and kilohertz repetition rates at 1030 and 1558 nm. Our work demonstrates broadband sub-bandgap saturable absorption of a single, solution processed WS2-SA, providing new potential efficacy for WS2 in ultrafast photonic applications.

A photodetector based on 2D non‐layered materials can easily utilize the photogating effect to achieve considerable photogain, but at the cost of response speed. Here, a rationally designed tunneling heterojunction fabricated by vertical stacking of non‐layered In2S3 and Te flakes is studied systematically. The Te/In2S3 heterojunctions possess type‐II band alignment and can transfer to type‐I or type‐III depending on the electric field applied, allowing for tunable tunneling of the photoinduced carriers. The Te/In2S3 tunneling heterojunction exhibits a reverse rectification ratio exceeding 104, an ultralow forward current of 10−12 A, and a current on/off ratio over 105. A photodetector based on the heterojunctions shows an ultrahigh photoresponsivity of 146 A W−1 in the visible range. Furthermore, the devices exhibit a response time of 5 ms, which is two and four orders of magnitude faster than that of its constituent In2S3 and Te. The simultaneously improved photocurrent and response speed are attributed to the direct tunneling of the photoinduced carriers, as well as a combined mechanism of photoconductive and photogating effects. In addition, the photodetector exhibits a clear photovoltaic effect, which can work in a self‐powered mode.