▎ 摘　　要

Hybrid nanostructures combining semiconductor quantum dots and graphene are attracting increasing attention because of their optoelectronic properties promising for photovoltaic applications. We present a hot-injection synthesis of a colloidal nanostructure which we define as quasi core/shell PbS/graphene quantum dots due to the incomplete passivation of PbS surfaces with an ultrathin layer of graphene. Simulation by density functional theory of a prototypical model of a nonstoichiometric Pb-rich core (400 atoms) coated by graphene (20 atoms for each graphene sheet) indicates the possibility of surface passivation of (111) planes of PbS with graphene resulting in a decrease in trap states and recombination sites. The graphene coating of the PbS quantum dots decreases the exciton lifetime up to 0.78 mu s as compared to 1.2 mu s for the oleic acid passivated PbS quantum dots due to the fast extraction of carriers. We have employed PbS/graphene as well as Cd-doped PbS/graphene quantum dots as active layers of bulk heterojunction solar cells, and we achieved solar power conversion efficiencies of 3.6 and 4.1%, respectively.