Colloidal quantum dots (CQDs) are attractive absorber materials for high-efficiency photovoltaics because of their facile solution processing,bandgap tunability due to quantum confinement effect,and multi-exciton generation.To date,all published performance records for PbS CQDs solar cells have been based on the conventional hot-injection synthesis method.This method usually requires relatively strict conditions such as high temperature and the utility of expensive source material (pyrophoric bis(trimethylsilyl) sulfide (TMS-S)),limiting the potential for large-scale and low-cost synthesis of PbS CQDs.Here we report a facile room-temperature synthetic method to produce high-quality PbS CQDs through inexpensive ionic source materials including Pb(NO3)2 and Na2S in the presence of triethanolamine (TEA) as the stabilizing ligand.The PbS CQDs were successfully prepared with an average particle size of about 5 nm.Solar cells based on the as-synthesized PbS CQDs show a preliminary power conversion efficiency of 1.82％.This room-temperature and low-cost synthesis of PbS CQ Ds will further benefit the development of solution-processed CQD solar cells.