Defect Control And Broadband Light-emitting Properties Of Monolayer WS₂

Single-layer tungsten disulfide?1L-WS₂?is an important two-dimensional semiconductor material with a wide direct band gap and unique optoelectronic properties.In field effect transistors?FETs?,light-emitting diodes?LEDs?,solar cells,phototransistors?FEpTs?,photodetectors and other aspects have been widely used.Carbon Quantum Dot?CQD?is a new type of zero-dimensional nanomaterial with high quantum yield and stable optical properties.They are used in many fields such as medical imaging technology,environmental monitoring,chemical analysis,catalyst preparation,and energy development,etc.,and have a good application prospect.In this paper,we first used vapor transport routine?VT?to prepare 1L-WS₂ with sulfur vacancy defects.The influence of intrinsic defects to the PL and resonant Raman spectroscopy of VT-deposited 1L-WS₂ were studied.We identified distinct PL emission spectra in 1L-WS₂ samples with increasing density of defects.The unexpected Raman intensity variations of LA?M?,2LA?M?and A1'???phonon modes of different samples measured at different temperatures can be well understood by considering the role of defects in mediating the excitonic energies.Then,the interaction between CQDs and 1L-WS₂ was studied.We prepared nitridized CQDs and 1L-WS₂ hybridized structures using CQDs with strong optical absorption and PL in the 500-600 nm light region.CQDs with varying levels of nitridization all behave as p-type dopants but abnormally quench the 1L-WS₂ PL intensity by over 70%.For the hybridized samples,the PL lifetimes of both CQDs and 1L-WS₂ are all reduced.Such a phenomenon can be successfully interpreted by an interactive NRET effect.Finally,we used a completely new method to prepare the WS₂ sample——EuC13 catalysis.Through the analysis of the fluorescence photo,we verified that the Eu element was doped into the lattice of WS₂.