The influence of solvent refractive index on the photoluminescence decay of thick‐shell gradient‐alloyed colloidal quantum dots investigated in a wide range of delay times

Abstract

AbstractColloidal semiconductor quantum dots have many potential optical applications, including quantum dot light‐emitting diodes, single‐photon sources, or biological luminescent markers. The optical properties of colloidal quantum dots can be affected by their dielectric environment. This study investigated the photoluminescence (PL) decay of thick‐shell gradient‐alloyed colloidal semiconductor quantum dots as a function of solvent refractive index. These measurements were conducted in a wide range of delay times to account for both the initial spontaneous decay of excitons and the delayed emission of excitons that has the form of a power law. It is shown that whereas the initial spontaneous PL decay is very sensitive to the refractive index of the solvent, the power‐law delayed emission of excitons is not. Our results seem to exclude the possibility of carrier self‐trapping in the considered solvents and suggest the existence of trap states inside the quantum dots. Finally, our data show that the average exciton lifetime significantly decreases as a function of the solvent refractive index. The change in exciton lifetime is qualitatively modeled and discussed.