Layer-Dependent Photoinduced Electron Transfer in 0D–2D Lead Sulfide/Cadmium Sulfide–Layered Molybdenum Disulfide Hybrids

We demonstrate layer-dependent electron transfer between core/shell PbS/CdS quantum dots (QDs) and layered MoS2 via energy band gap engineering of both the donor (QDs) and the acceptor (MoS2) components. We do this by (i) changing the size of the QD or (ii) by changing the number of layers of MoS2, and each of these approaches alters the band gap and/or the donor–acceptor separation distance, thus providing a means of tuning the charge-transfer rate. We find the charge-transfer rate to be maximal for QDs of smallest size and for QDs combined with a 5-layer MoS2 or thicker. We model this layer-dependent charge-transfer rate with a theoretical model derived from Marcus theory previously applied to nonadiabatic electron transfer in weakly coupled systems by considering the QD transferring photogenerated electrons to noninteracting monolayers within a few layers of MoS2.