graphene, however, is problematic for many optoelectronic applications. Semiconducting layered metal dichalcogenides (LMDs) have generated an immense amount of interest, owing to their specific bandgaps in the ≈1-2.4 eV range. [2] Most LMDs undergo a transition from an indirect bandgap material in the multilayer form to a direct bandgap material in the monolayer form and exhibit strong lightmatter interaction at the 2D limit. [3,4] All of these features make 2D LMDs promising materials for several applications, such as transistors [5] and optoelectronic [6] and valleytronic [7] devices. Nonetheless, the finite bandgap of such reported LMDs largely restricts their applications in IR and ultraviolet (UV) photodetection. [8] UV photodetection, particularly in the solar blind range (200 to 280 nm), has great potential in the missile detection, flame alarms, and so forth. However, the lack of wide bandgap LMD materials makes realizing 2D UV photodetectors a challenge.As a new important member of the LMD family, germanium diselenide (GeSe 2 ), with a direct wide bandgap, has many potential applications in UV detection and IR waveguides. [9] Moreover, GeSe 2 exhibits a monoclinic crystal structure, [10] within two crystallographically different types of GeSe 4/2 tetrahedra centered on the Ge1 and Ge2 atoms, as shown in As an important 2D layered metal dichalcogenide, germanium diselenide (GeSe 2 ) with a direct wide bandgap is attracting increasing attention for its potential applications in ultraviolet (UV) detection. However, only few-layer GeSe 2 has been reported to date. Here, a joint theoretical-experimental study on the optical and electronic properties of monolayer GeSe 2 is presented, and monolayer GeSe 2 is shown to have a direct wide bandgap of 2.96 eV. Consequently, monolayer GeSe 2 does not respond to a major fraction of the visible spectrum. Notably, the photofield effect transistors based on the GeSe 2 monolayer show p-type behavior, high responsivity, superior detectivity, and a fast response time, competitive with state-of-the-art UV detectors. In addition to the excellent photoresponse properties, 2D GeSe 2 crystals also exhibit perpendicular optical reversal of the linear dichroism and polarized photodetection under wavelength modulation. Theoretical calculations of the band structure are used to shed light on these experimental results. The findings suggest that 2D GeSe 2 is a promising candidate for highly selective polarization-sensitive UV detection.

We have demonstrated that the embedded Ag nanowire network plays the important role of greatly improving responsivity and shortening response time in ZnO/Ag nanowires/ZnO composite uv photodetector.

High performance photodetectors based on van der Waals heterostructures (vdWHs) are crucial to developing micro-nano-optoelectronic devices. However, reports show that it is difficult to balance fast response and high sensitivity. In this work, we design a photovoltaic field-effect photodiode (PVFED) based on the WSe2/MoS2/WSe2 double vdWHs, where the photovoltage that originated from one vdWH modulates the optoelectronic characteristics of another vdWH. The proposed photodiode exhibits an excellent self-powered ability with a high responsivity of 715 mA·W–1 and fast response time of 45 μs. This work demonstrates an efficient method that optimizes the photoelectric performance of vdWH by introducing the photovoltaic field effect.

In conjugated polymer based photovoltaic devices, efficient charge transfer and photostability of the fluorescence polymer are two essential properties, which could be responsible for better performance and longer lifetime of the device. Hence, it is of great importance to explore strategies that can enhance the exciton separation and improve the photostability of polymers. In this work, composites of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) participated by appropriate amounts of reduced graphene oxide (r-GO), which leads to a significant photoluminescence quenching as well as superior photostability of MEH-PPV, have been investigated. The photoluminescence quenching and photostability of MEH-PPV/r-GO composites have been observed by UV–visible and fluorescence spectroscopy. From transient fluorescence spectrum, the mechanism of photoluminescence quenching has been confirmed to be static quenching, which is caused by electron transfer at the interface of the composite. Furthermore, we propose that this very efficient photoinduced excitation electron transfer from MEH-PPV to r-GO results in protecting MEH-PPV from further chemical degradation reaction. This work shows that graphene is promising as both an electron acceptor and light stabilizer for applications in optoelectronics devices.