Van der Waals (vdW) heterodiodes based on two-dimensional (2D) materials have shown tremendous potential in photovoltaic detectors and solar cells. However, such 2D photovoltaic devices are limited by low quantum efficiencies due to the severe interface recombination and the inefficient contacts. Here, we report an efficient MoS₂/AsP vdW hetero-photodiode utilizing a unilateral depletion region band design and a narrow bandgap AsP as an effective carrier selective contact. The unilateral depletion region is verified via both the Fermi level and the infrared response measurements. The device demonstrates a pronounced photovoltaic behavior with a short-circuit current of 1.3 μA and a large open-circuit voltage of 0.61 V under visible light illumination. Especially, a high external quantum efficiency of 71%, a record high power conversion efficiency of 9% and a fast response time of 9 μs are achieved. Our work suggests an effective scheme to design high-performance photovoltaic devices assembled by 2D materials.

Nickel cobalt sulfide (NiCo ₂ S ₄ ) is a promising battery-type material for electrochemical energy storage.

Printed electronic technologies draw tremendous attention worldwide due to their ability to surpass the limitations of traditional high-cost electronics, based on rigid silicon, and the manufacturing of various devices on flexible substrates. As a critical component of flexible electronics, electrodes fabricated on soft, bendable, and stretchable substrates are of great importance. Based on the fabrication process, this paper classifies the mainstream technologies into two categories: top-down and bottom-up. Top-down technologies include physical evaporation methods, printing technologies and soft lithography, while bottom-up technologies involve polymer-assisted-metal-deposition methods and ion-exchange methods, respectively. In contrast to top-down technologies that transfer functional ink onto substrates directly, the bottom-up method achieves a great improvement in the adhesion between substrates and metal electrodes. In this paper, the challenges of top-down technologies, including cost, synthesis, and choice of ink for printing technologies, the limited choice of metal for bottom-up technologies and the mass production of these methods, are also discussed.