Electron migration optimization through nanostructural control of hierarchical Fe3O4 based counter electrodes for high-performance dye-sensitized solar cells

Reasonably designing of counter electrode (CE) and iodine ion electrolyte is crucial for enhancing the power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs). Fe 3 O 4 possesses high conductivity and catalytic activity to facilitate the electrolyte reduction reaction at the surface of CE. However, the morphology control and active site modulation of Fe 3 O 4 based CE are still to be explored. Herein, we propose a facile bottom-top strategy to prepare hierarchical Fe 3 O 4 nanostructures with different tunable morphologies, including Fe 3 O 4 nanorings (NR), nanosheets (NS) and nanoflowers (NF). Electrochemical impedance spectroscopy , Tafel polarization, cyclic voltammetry and photocurrent density-voltage measurements of these samples were carried out, revealing their high performances as CE in DSSCs. Among them, the Fe 3 O 4 NF with mesoporous nanosphere flower structure and high specific surface area is synthesized, which realized the highest PCE (8.56%), which is also higher than the value of Pt based CE (7.57%). Compared to other competing materials, Fe 3 O 4 nanostructure based CE shows the outstanding merits of high photovoltaic performance , easy preparation, low cost and eco-friendliness, offering the possibility to replace conventional Pt based CE in DSSCs.