CdSe x S1−x /CdS-cosensitized 3D TiO2 hierarchical nanostructures for efficient energy conversion

Three-dimensional TiO 2 hierarchical nanostructures (3D-TiO 2 -HNs) containing TiO 2 nanotrees and nest-like hollow spheres were synthesized and used as backbones for CdSe x S 1− x quantum dot (QD) loading. These CdSe x S 1− x QD-sensitized 3D-TiO 2 -HNs were then used as photoelectrodes in the preparation of quantum-dot-sensitized solar cells. As revealed by TEM images, the highly porous 3D-TiO 2 -HNs represent an excellent framework on which to deposit a large number of CdSe x S 1− x QDs in order to form homogeneous and compact CdSe x S 1− x -sensitized layers in photoelectrodes using a spin-assisted successive ionic layer adsorption and reaction method (spin-SILAR). Following careful adjustment of the molar ratio of Se 2− to S 2− , the number of spin-SILAR cycles, and the thickness of the CdS passivation layer used, the best-performing QDSC was shown to yield a short-circuit current density of 18.22 mA cm −2 , an open-circuit voltage of 0.520 V, a fill factor of 0.510, and a power conversion efficiency of 4.83%. This high performance is possible because the device is able to absorb a relatively broad range of wavelengths and because charge recombination is suppressed in the device.