Lewis acid-doped transition metal dichalcogenides for ultraviolet–visible photodetectors

Ultraviolet photodetectors(UV PDs)are widely used in civilian,scientific,and military fields due to their high sensitivity and low false alarm rates.We present a temperature-dependent Lewis acid p-type doping method for transition metal dichalcogenides(TMDs),which can effectively be used to extend the optical response range.The p-type doping based on surface charge transfer involves the chemical adsorption of the Lewis acid SnCl_(4)as a light absorption layer on the surface of WS_(2),significantly enhancing its UV photodetection performance.Under 365 nm laser irradiation,WS_(2)PDs exhibit response speed of 24 ms/20 ms,responsivity of 660 mA/W,detectivity of 3.3×10^(11)Jones,and external quantum efficiency of 226%.Moreover,we successfully apply this doping method to other TMDs materials(such as MoS_(2),MoSe_(2),and WSe_(2))and fabricate WS_(2) lateral p–n heterojunction PDs.

Spatially selective p-type doping for constructing lateral WS_(2) p-n homojunction via low-energy nitrogen ion implantation

The construction of lateral p-n junctions is very important and challenging in two-dimensional(2D)semiconductor manufacturing process.Previous researches have demonstrated that vertical p-n junction can be prepared simply by vertical stacking of 2D materials.However,interface pollution and large area scalability are challenges that are difficult to overcome with vertical stacking technology.Constructing 2D lateral p-n homojunction is an effective strategy to address these issues.Spatially selective p-type doping of 2D semiconductors is expected to construct lateral p-n homojunction.In this work,we have developed a low-energy ion implantation system that reduces the implanted energy to 300 eV.Low-energy implantation can form a shallow implantation depth,which is more suitable for modulating the electrical and optical properties of 2D materials.Hence,we utilize low-energy ion implantation to directly dope nitrogen ions into few-layer WS_(2) and successfully realize a precise regulation for WS_(2) with its conductivity type transforming from n-type to bipolar or even p-type conduction.Furthermore,the universality of this method is demonstrated by extending it to other 2D semiconductors,including WSe_(2),SnS_(2) and MoS_(2).Based on this method,a lateral WS_(2) p-n homojunction is fabricated,which exhibits significant rectification characteristics.A photodetector based on p-n junction with photovoltaic effect is also prepared,and the open circuit voltage can reach to 0.39 V.This work provides an effective way for controllable doping of 2D semiconductors.

Recent progress about 2D metal dichalcogenides: Synthesis and application in photodetectors

In recent years, two-dimensional (2D) layered metal dichalcogenides (MDCs) have received enormous attention on account of their excellent optoelectronic properties. Especially, various MDCs can be constructed into vertical/lateral heterostructures with many novel optical and electrical properties, exhibiting great potential for the application in photodetectors. Therefore, the batch production of 2D MDCs and their heterostructures is crucial for the practical application. Recently, the vapour phase methods have been proved to be dependable for growing large-scale MDCs and related heterostructures with high quality. In this paper, we summarize the latest progress about the synthesis of 2D MDCs and their heterostructures by vapour phase methods. Particular focus is paid to the control of influence factors during the vapour phase growth process. Furthermore, the application of MDCs and their heterostructures in photodetectors with outstanding performance is also outlined. Finally, the challenges and prospects for the future application are presented.

Intrinsic defects of nonprecious metal electrocatalysts for energy conversion: Synthesis, advanced characterization, and fundamentals

With the depletion of fossil fuels and environmental pollution, energy storage and conversion have become the focus of current research. Water splitting and fuel cell technologies have made outstanding contributions to energy conversion. However, the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) have slow kinetics, which limit the capacity of fuel cells. It is of great significance to develop catalysts for the OER and ORR and continuously improve their catalytic performance. Many studies have shown that intrinsic defects, especially vacancies (anion and cation vacancies), can effectively improve the efficiency of electrochemical energy storage and conversion. The introduction of intrinsic defects can generally expose more active sites, enhance conductivity, adjust the electronic state, and promote ion diffusion, thereby enhancing the catalytic performance. This review comprehensively summarizes the latest developments regarding the effects of intrinsic defects on the performance of non-noble metal electrocatalysts. According to the type of intrinsic defect, this article reviews in detail the regulation mechanism, preparation methods and advanced characterization techniques of intrinsic defects in different materials (oxides, non-oxides, etc.). Then, the current difficulties and future development of intrinsic defect regulation are analyzed and discussed thoroughly. Finally, the prospect of intrinsic defects in the field of electrochemical energy storage is further explored.