The van der Waals heterojunctions of 2D materials offer tremendous opportunities in designing and investigating multifunctional and high-performance electronic and optoelectronic devices. In this study, a vertical p-n diode is constructed by vertically stacking p-type few-layer black phosphorus (BP) on n-type few-layer indium selenide (InSe). The photodetector based on the heterojunction displays a broadband and gate-modulated photoresponse under illumination. More importantly, by taking advantage of the strong linear dichroism of BP, the device demonstrates a highly polarization-sensitive photocurrent with an anisotropy ratio as high as 0.83. Additionally, the device can function in a zero-bias photovoltaic mode, enabling a fast photoresponse and low dark current. The external quantum efficiency can reach ≈3%, which is impressive for BP-based devices. The results pave the way for the implementation of p-BP/n-InSe heterostructure as a promising candidate for future multifunctional optoelectronics and, especially, polarization-sensitive applications.

Low-symmetry layered materials such as black phosphorus (BP) have been revived recently due to their high intrinsic mobility and in-plane anisotropic properties, which can be used in anisotropic electronic and optoelectronic devices.

DW MR imaging is useful for differentiating BEOTs from MEOTs. Patients with BEOTs are treated differently from patients with MEOTs. Conservative fertility-sparing laparoscopic surgery can be performed in patients with BEOTs. BEOTs often affect young women of childbearing age.

Recently, the emerging conceptual valley-related devices have attracted much attention due to the progress on generating, controlling, and detecting the valley degree of freedom in the transition metal dichalcogenide (TMD) monolayers. In general, it is known that achieving valley degree of freedom with long valley lifetime is crucial in the implementation of valleytronic devices. Here, we provide a brief introduction of the basic understandings of valley degree of freedom. We as well review the recent experimental advancement in the modulation of valley degree of freedom. The strategies include optical/magnetic/electric field tuning, moiré patterns, plasmonic metasurface, defects and strain engineering. In addition, we summarize the corresponding mechanisms, which can help to obtain large degree of polarization and long valley lifetimes in monolayer TMDs. Based on these methods, two-dimensional valley-optoelectronic systems based on TMD heterostructures can be constructed, providing opportunities for such as the new paradigm in data processing and transmission. Challenges and perspectives on the development of valleytronics are highlighted as well.