Substrate placement angle-dependent growth of dandelion-like TiO₂ nanorods for solid-state semiconductor-sensitized solar cells

Hierarchical nanostructures grown directly on transparent conducting oxides hold the promise of overcoming the limitations of current semiconductor-sensitized solar cells based on random networks of nanoparticles. Here, we develop a facile substrate placement angle-dependent hydrothermal process to grow dandelion-like TiO₂ nanostructures directly on transparent conductive oxides. TiO₂ nanocrystals grown in solution during the synthesis process are found to promote the dandelion-like structure. By using these TiO₂ nanostructures as photoanodes, Sb₂S₃ as the sensitizer, and P3HT as the hole-transporting material, we demonstrate fabrication of all-solid-state semiconductor-sensitized solar cells, which yield solar power conversion efficiency up to 4.71%. Electrochemical impedance spectroscopy indicates that moderate rod fusion at the base beneficially reduces electron recombination in the device. This work provides an innovative method for growing branched, one-dimensional TiO₂ nanostructures that can be used for energy harvesting and storage.