Pressure manipulation of ultrafast carrier dynamics in monolayer WS_(2)

Two-dimensional transition metal dichalcogenides(TMDs)have intriguing physic properties and offer an exciting platform to explore many features that are important for future devices.In this work,we synthesized monolayer WS_(2)as an example to study the optical response with hydrostatic pressure.The Raman results show a continuous tuning of the lattice vibrations that is induced by hydrostatic pressure.We further demonstrate an efficient pressure-induced change of the band structure and carrier dynamics via transient absorption measurements.We found that two time constants can be attributed to the capture process of two kinds of defect states,with the pressure increasing from 0.55 GPa to 2.91 GPa,both of capture processes were accelerated,and there is an inflection point within the pressure range of 1.56 GPa to 1.89 GPa.Our findings provide valuable information for the design of future optoelectronic devices.

Radiation-pressure-induced photoluminescence enhancement of all-inorganic perovskite CsPbBr3 quantum dots

Perovskite quantum dots(QDs) are of great interest due to their outstanding optoelectronic properties and tremendous application potential. Improving photoluminescence(PL) spectra in all-inorganic perovskite QDs is of great importance for performance enhancement. In this work, the PL quantum yield of the CsPbBr3 perovskite QDs is enhanced from 70% to 95% with increasing radiation pressure. Such enhancement is attributed to the increased binding energy of self-trapped excitons(STEs) upon radiation pressure, which is consistent with its blue-shifted PL and other characterization results. Furthermore, we study ultrafast absorption spectroscopy and find that the dynamics of relaxation from free excitons to STEs in radiation pressure CsPbBr3 QDs is ascribed to stronger electron–phonon coupling in the contracted octahedral structure. It is further demonstrated that radiation pressure can boost the PL efficiency and explore effectively the relationship between the structure and optical properties.