Enhanced photoelectrochemical performance of CdSe/CdS/TiO2 nanorod arrays solar cell with a PbS underlayer

Vertically oriented single-crystalline one-dimensional (1D) TiO2 nanorod arrays film with high aspect ratio was synthesized directly on transparent fluorine-doped tin oxide conducting glass substrate by a facile two-step hydrothermal process. When used in CdSe/CdS/PbS quantum dots sensitized solar cells (QDSSCs), the 1D ordered TiO2 nanorods with the increased internal surface areas can adsorb more QDs, which enhanced the ability of light absorption. Moreover, 1D ordered TiO2 nanorods can also offer a direct electrical pathway for photogenerated electrons, accelerating the electrons transfer rate. In addition, the introduction of PbS as underlayer in CdSe/CdS/TiO2 system can extend the optical absorption range, which greatly raised the utilization of the solar energy. The incident photon to current conversion efficiency of the CdSe/CdS/PbS/TiO2 nanorods solar cell reached to 52 %, which is higher than that of CdSe/CdS/TiO2 nanorods solar cell, indicating that the better light harvesting ability could be obtained by the introduction of PbS QDs. The power conversion efficiency of CdSe/CdS/PbS/TiO2 nanorods solar cell can reach to 2.56 % under one sun illumination (AM 1.5 G, 100 mW/cm(2)), which is greatly higher than that of CdSe/CdS/TiO2 nanorods solar cell (1.73 %).