Heterogeneous system synthesis of high quality PbS quantum dots for efficient infrared solar cells

As promising optoelectronic materials, lead sulfide quantum dots (PbS QDs) have attracted great attention. However, their applications are substantially limited by the QD quality and/or complicated synthesis. Herein, a facile new synthesis is developed for highly monodisperse and halide passivated PbS QDs. The new synthesis is based on a heterogeneous system containing a PbCl₂-Pb(OA)₂ solid-liquid precursor solution. The solid PbCl₂ inhibits the diffusion of monomers and maintains a high oversaturation condition for the growth of PbS QDs, resulting in high monodispersities. In addition, the PbCl₂ gives rise to halide passivation on the PbS QDs, showing excellent stability in air. The high monodispersity and good passivation endow these PbS QDs with outstanding optoelectronic properties, demonstrated by a 9.43% power conversion efficiency of PbS QD solar cells with a bandgap of ~ 0.95 eV (1,300 nm). We believe that this heterogeneous strategy opens up a new avenue optimizing for the synthesis and applications of QDs.