Excitons dynamic modulation by tailoring size of high-entropy Mo0.64W0.36S2 alloy

Two-dimensional transition metal disulfides with tailored optical response are vital to demonstrate versatile optoelectronic devices and nanophotonic elements. In this work, using transient absorption spectroscopy in conjunction with density functional theory calculations, we demonstrate ultrafast excitons absorption modulation via tailoring the size of a transition-metal dichalcogenide alloy Mo0.64W0.36S2 nanosheet. As the size of the nanosheet increases from 9 +/- 5 to 190 +/- 121 nm, peak positions of the A and B excitons vary from 666 to 675nm and 626 to 638 nm, respectively. Furthermore, the decay lifetimes of A excitons slow down from 1.16 to 1.84 ps when the size changes from 9 +/- 5 to 190 +/- 121 nm. It is shown that the exciton diffusion and decay properties can be modulated by the components and structure modulation, which is beneficial for the optimal design and optimization of optoelectronic devices.