2D Lead Dihalides for High‐Performance Ultraviolet Photodetectors and their Detection Mechanism Investigation

2D halide semiconductors, a new family of 2D materials in addition to transition metal dichalcogenides, present ultralow dark current and high light conversion yield, which hold great potential in photoconductive detectors. Herein, a facile aqueous solution method is developed for the preparation of large‐scale 2D lead dihalide nanosheets (PbF_2‐xI_x). High‐performance UV photodetectors are successfully implemented based on 2D PbF_2‐xI_x nanosheets. By modulating the components of halogens, the bandgap of PbF_2‐xI_x nanosheets can be tuned to meet varied detection spectra. The photoresponse dependence on incident power density, wavelength, detection environment, and temperature are systematically studied to investigate their detection mechanism. For PbI₂ photodetectors, they are dominantly driven by a photoconduction mechanism and show a fast response speed and a low noise current density. A high normalized detectivity of 1.5 × 10¹² Jones and an I_ON/I_OFF ratio up to 10³ are reached. On the other hand, PbFI photodetectors demonstrate a photogating mechanism mediated by trap states showing high responsivity. The novel 2D halide materials with wide bandgaps, superior detection performance, and facile synthesis process can enrich the Van der Waals solids family and hold great potential for a wide variety of applications in advanced optoelectronics.     

Flexible and High‐Performance All‐2D Photodetector for Wearable Devices

Emerging novel applications at the forefront of innovation horizon raise new requirements including good flexibility and unprecedented properties for the photoelectronic industry. On account of diversity in transport and photoelectric properties, 2D layered materials have proven as competent building blocks toward next‐generation photodetectors. Herein, an all‐2D Bi₂Te₃‐SnS‐Bi₂Te₃ photodetector is fabricated with pulsed‐laser deposition. It is sensitive to broadband wavelength from ultraviolet (370 nm) to near‐infrared (808 nm). In addition, it exhibits great durability to bend, with intact photoresponse after 100 bend cycles. Upon 370 nm illumination, it achieves a high responsivity of 115 A W^?1, a large external quantum efficiency of 3.9 × 10⁴%, and a superior detectivity of 4.1 × 10¹¹ Jones. They are among the best figures‐of‐merit of state‐of‐the‐art 2D photodetectors. The synergistic effect of SnS's strong light–matter interaction, efficient carrier separation of Bi₂Te₃–SnS interface, expedite carrier injection across Bi₂Te₃–SnS interface, and excellent carrier collection of Bi₂Te₃ topological insulator electrodes accounts for the superior photodetection properties. In summary, this work depicts a facile all‐in‐one fabrication strategy toward a Bi₂Te₃‐SnS‐Bi₂Te₃ photodetector. More importantly, it reveals a novel all‐2D concept for construction of flexible, broadband, and high‐performance photoelectronic devices by integrating 2D layered metallic electrodes and 2D layered semiconducting channels.