PbS quantum dots (QDs), prepared by the successive ionic layer adsorption and reaction (SILAR) method, are incorporated in perovskite solar cells based on CH3NH3PbI3. Enhanced light absorption in the wavelength range of 330-1400 nm is observed, and the cell prepared with 2 SILAR coating cycles exhibits the best photovoltaic performance. It is observed that the PbS QDs can reduce the TiO2 decomposition damage to the CH3NH3PbI3 films and promote the stability of the modified perovskite solar cells. Charge transfer dynamics in the perovskite solar cells is studied with intensity modulated photocurrent/photovoltage spectroscopy, and improved charge diffusion lengths are obtained for the modified cells, with the best value of 0.86 mu m obtained for the device prepared with 2 SILAR coating cycles. This improvement could be attributed to the enhanced electron transport and reduced electron recombination processes in the device structures after incorporating PbS QDs. (C) 2015 Elsevier B.V. All rights reserved.