High-efficiency dye-sensitized solar cells with hierarchical structures titanium dioxide to transfer photogenerated charge

• Hierarchical TiO2 nanorod-sheet-flowers were synthesized on FTO using NaOH-assisted hydrothermal method.
• The novel nanostructure exhibited efficient electron transfer with better light harvesting and dye adsorption abilities.
• 0.3 mL of added TBT is appropriate for TiO2 nanorod-flowers to obtain PCE above 6.83%.
• Efficiency of TiO2 nanorod-sheet-flowers based DSSC was 8.41%, 51.8% higher than that of P25 photoanode.

Hierarchical TiO2 nanorod-sheet-flowers (TNRSFs) consisting of one dimensional (1D) vertically aligned rutile TiO2 nanorods array (TNRA), 2D TiO2 nanosheets (TNSs) and 3D TiO2 nanoflowers (TNFs) have been synthesized via a simple NaOH-assisted hydrothermal method and employed as an photoanode for high-efficiency dye-sensitized solar cells (DSSCs). In our strategy, The TNFs layer with large thickness can potentially enable a great amount of dye adsorption and significantly strengthen the light-harvesting ability, which is beneficial for generating more charge. In addition, The TNRA and TNSs act like charge collectors, providing efficient transport pathways for electrons, which means the photogenerated charge can be collected efficiently through this conducting network. The electrochemical impedance spectroscopy (EIS) measurement shows that the TNRSF film possesses better electron transport ability and longer electron lifetime (28.4 ms) compared with the TiO2 nanoparticals (TNPs) film. Furthermore, an overall power conversion efficiency of 8.41% (with a Jsc of 16.95 mA cm−2, Voc of 0.73 V and FF of 68%) is achieved for the DSSC based on the TNRSF photoanode, indicating a 51.8% enhancement compared with that of the TNPs photoanode (5.54%). The discoveries from this work highlight the significance of designing photoanode materials with hierarchical structures for enhanced photovoltaic performance.