Strong suppression of emission quenching in core quantum dots coupled to monolayer MoS2

Non-radiative processes like energy and charge transfer in 0D-2D semiconductor quantum dot (QD)-transition metal dichalcogenide (TMD) and other two dimensional layered materials, like graphene and analogs, leading to strong quenching of the photoluminescence (PL) of the usually highly emissive QDs, have been widely studied. Here we report control of emission efficiency of core QDs placed in close proximity to monolayers of MoS2. The QDs are transferred in the form of a high density compact monolayer with the dot-dot separation, d as well as the MoS2-QD separation, d, being controlled through chemical methods. While at larger separations we observe some quenching due to non radiative processes at smaller separations we observe enhanced emission from QDs on MoS2 as compared to reference despite the presence of significant nonradiative charge transfer. Interestingly, at small separations d, we see evidence of strong dotdot interaction and significant red shift of QD PL which enhances spectral overlap with the B exciton of MoS2. However, we observe significant reduction of PL quenching of QD relative to longer d and d case, despite increased probability of non-radiative resonant energy transfer to MoS2, due to the enhanced spectral overlap, as well as charge transfer. Significantly we observe that simultaneously the intensity of the B exciton of MoS2 increases significantly suggesting the possibility of coherent and resonant radiative energy exchange between the 0D excitons in QDs and the 2D B exciton in MoS2. Our study reveals interesting nanoscale light-matter interaction effects which can suppress quenching of QDs leading to potential applications of these nanoscale materials in light emitting and photonic devices.