Reduced Dielectric Screening and Enhanced Energy Transfer in Single- and Few-Layer MoS2

We report highly efficient non-radiative energy transfer from cadmium selenide (CdSe) quantum dots to monolayer and few-layer molybdenum disulfide (MoS2). The quenching of the donor quantum dot photoluminescence increases as the MoS2 flake thickness decreases, with the highest efficiency (>95%) observed for monolayer MoS2. This counterintuitive result arises from reduced dielectric screening in thin layer semiconductors having unusually large permittivity and a strong in-plane transition dipole moment, as found in MoS2. Excitonic energy transfer between a 0D emitter and a 2D absorber is fundamentally interesting and enables a wide range of applications including broadband optical down-conversion, optical detection, photovoltaic sensitization, and color shifting in light-emitting devices.