Stability,electronic structure,and optical properties of lead-free perovskite monolayer Cs3B2X9(B=Sb,Bi;X=Cl,Br,I)and bilayer vertical heterostructure Cs_(3)B_(2)X_(9)/Cs3B’2X9(B,B’=Sb,Bi;X=Cl,Br,I)

The lead-free perovskites Cs_(3)B_(2)X_(9)(B=Sb,Bi;X=Cl,Br,I)as the popular photoelectric materials have excellent optical properties with lower toxicity.In this study,we systematically investigate the stable monolayer Cs_(3)B_(2)X_(9)and bilayer vertical heterostructure Cs_(3)B_(2)X_(9)/Cs3B02X9(B,B0=Sb,Bi;X=Cl,Br,I)via first-principles simulations.By exploring the electrical structures and band edge positions,we find the band gap reduction and the band type transition in the heterostructure Cs_(3)B_(2)X_(9)/Cs3B02X9 due to the charge transfer between layers.Furthermore,the results of optical properties reveal light absorption from the visible light to UV region,especially monolayer Cs3Sb2I9 and heterostructure Cs3Sb2I9/Cs3Bi2I9,which have absorption peaks in the visible light region,leading to the possibility of photocatalytic water splitting.These results provide insights for more two-dimensional semiconductors applied in the optoelectronic and photocatalytic fields.

High-performance optoelectronic devices based on van der Waals vertical MoS2/MoSe2 heterostructures

Monolayer MoS2 is a direct band gap semiconductor with large exciton binding energy,which is a promising candidate for the application of ultrathin optoelectronic devices.However,the optoelectronic performance of monolayer M0S2 is seriously limited to its growth quality and carrier mobility.In this work,we report the direct vapor growth and the optoelectronic device of verticallystacked MoS2/MoSe2 heterostructure,and further discuss the mechanism of improved device performance.The optical and high-resolution atomic characterizations demonstrate that the heterostructure interface is of high-quality without atomic alloying.Electrical transport measurements indicate that the heterostructure transistor exhibits a high mobility of 28.5 cm^2/(V·s)and a high on/off ratio of 10^7.The optoelectronic characterizations prove that the heterostructure device presents an enhanced photoresponsivity of 36 A/W and a remarkable detectivity of 4.8×10^11 Jones,which benefited from the interface induced built-in electric field and carrier dependent Coulomb screening effect.This work demonstrates that the construction of two-dimensional(2D)semiconductor heterostructures plays a significant role in modifying the optoelectronic device properties of 2D materials.

Van der Waals epitaxial growth and optoelectronics of a vertical MoS_(2)/WSe_(2)p-n junction

Two-dimensional(2D)transition metal dichalcogenides(TMDs)have attracted extensive attention due to their unique electronic and optical properties.In particular,TMDs can be fexibly combined to form diverse vertical van der Waals(vdWs)heterostructures without the limitation of lattice matching,which creates vast opportunities for fundamental investigation of novel optoelectronic applications.Here,we report an atomically thin vertical p-n junction WSe_(2)/MoS_(2)produced by a chemical vapor deposition method.Transmission electron microscopy and steady-state photoluminescence experiments reveal its high quality and excellent optical properties.Back gate feld efect transistor(FET)constructed using this p-n junction exhibits bipolar behaviors and a mobility of 9 cm^(2)/(V·s).In addition,the photodetector based on MoS_(2)/WSe_(2)heterostructures displays outstanding optoelectronic properties(R=8 A/W,D^(*)=2.93×10^(11)Jones,on/of ratio of 10^(4)),which benefted from the built-in electric feld across the interface.The direct growth of TMDs p-n vertical heterostructures may ofer a novel platform for future optoelectronic applications.

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.