CdS/CdSe system of quantum dot co-sensitized solar cell is one of the most attractive structures for highefficiency due to its effect of adjusting level.However,the efficiencies recently achieved still have much room for improvement.Challenges in the quantum dot co-sensitized solar cell are the low absorption intensity and an unconspicuous stepped structure formed between levels of CdS and CdSe.Here we report an innovative concept for the rare-earth materials La doping of the CdS layer in the CdS/CdSe quantum dot co-sensitized solar cells by means of SILAR.The doping of CdS with La leads to enhanced absorption intensity,reduced bandgap,increased band of conduction and valence and consequently enhanced current density in the solar cell.Our results are a new exploration for solving challenges of quantum dot co-sensitized solar cell.