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

Abstract

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). Fe3O4 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 Fe3O4 based CE are still to be explored. Herein, we propose a facile bottom-top strategy to prepare hierarchical Fe3O4 nanostructures with different tunable morphologies, including Fe3O4 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 Fe3O4 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, Fe3O4 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.