The preparation and assembly of CdS_xSe_1−x alloyed quantum dots on TiO₂ nanowire arrays for quantum dot-sensitized solar cells

Highly ordered TiO₂ nanowire (NW) arrays were constructed by hydrothermal process as support materials for quantum dot sensitized solar cells (QDSSCs). The CdS_xSe_1−x alloyed quantum dots (QDs) with tunable composition have been assembled onto the TiO₂ NW arrays via a facile hydrothermal method to form CdS_xSe_1−x/TiO₂ NW photoanodes. The light absorption range of the CdS_xSe_1−x/TiO₂ NW photoanodes can be controlled by changing the atomic ratio of S to Se. Based on CdS_xSe_1−x/TiO₂ NW photoanodes, the photovoltaic performance of these CdS_xSe_1−x/TiO₂ NW solar cells gradually improved as the increase of Se content in CdS_xSe_1−x alloyed QDs. Among all sample CdS_xSe_1−x/TiO₂ NW solar cells which were prepared with different feed molar ratio of S:Se, the CdS_0.27Se_0.73/TiO₂ NW solar cell (prepared with S:Se = 0:4) produced the highest power conversion efficiency up to 2.46 %. The results of investigation into optical properties and incident photon-to-current conversion efficiency indicates that the enlarged light absorption range and effective photo-to-electrical efficiency can be obtained with Se-rich CdS_xSe_1−x/TiO₂ NW photoanodes, which contribute to the enhanced photovoltaic performance of the CdS_0.27Se_0.73/TiO₂ NW solar cell.