Photophysical Properties of Mn-Doped InP/ZnS Nanocrystals

InP-based nanocrystals (NCs) have received considerable attention as promising candidates to replace Cd- and Pb-based NCs because they contain no heavy metal elements. However, relevant studies on the photophysical properties of InP-based NCs are still insufficient. In this work, Mn-doped InP/ZnS NCs are synthesized, and their photophysical properties have been investigated. With the help of transient absorption spectrum measurement, it is found that Mn-doped InP/ZnS NCs exhibit efficient exciton–dopant exchange interaction. Through the temperature-dependent fluorescence lifetime measurements it is revealed that some excitons may undergo reverse crossing to the conduction band of the InP core from the long-lived 4T1 state of the Mn2+ ions with increasing temperature, resulting in the exciton fluorescence lifetime of the doped NCs to be less influenced by the temperature. In addition, compared with the Mn fluorescence, the exciton fluorescence shows an opposite intensity tendency to the temperature variation as a result of the greatly decreased energy transfer efficiency at elevated temperature. Importantly, the doped NCs exhibit a bright two-photon excited Mn fluorescence in which no size selection effect is observed. The excellent photophysical properties of Mn-doped InP/ZnS NCs imply that they are promising in the applications of highly effective optoelectronic devices and biological science.