Size-dependent interfacial coupling in mixed-dimensional CdSe quantum dot/monolayer WS₂ heterostructures

The characteristics of quantum dot (QD) size-dependent interfacial coupling in mixed-dimensional CdSe QD/monolayer WS₂ heterostructures are investigated through steady-state and excitation power-dependent photoluminescence (PL) measurements. Results show that for small QDs with a larger bandgap than WS₂, the exciton emission of WS₂ is significantly quenched with the emergence of a trion feature, which indicates that electron transfer occurs from QDs to WS₂. In contrast, large QDs with a smaller bandgap than WS₂ exhibit significant enhancement of QD PL and simultaneous suppression of WS₂ exciton emission, suggesting that Förster-type energy transfer occurs. Furthermore, the excitation power-law scaling of the WS₂ exciton intensity exhibits sublinear behavior in pristine monolayer WS₂ but becomes superlinear in QD/WS₂ heterostructures, regardless of QD size. These findings demonstrate that QD/WS₂ heterostructures enable controllable modification of both excitonic emission and electronic structure, and thus provide a versatile platform for optoelectronic applications based on engineered charge and energy transfer.