Electrophoretically Achieved Thick and High-Quality NiO Film as Photocathode for High-Performance P1-Based p‑DSSCs

This work demonstrates the first preparation of a NiO photocathode by electrophoretic deposition (EPD), with which high-quality and thickness-controllable thick/porous NiO films with a bandgap of about 3.8 eV were obtained. On the other hand, during the preparation of the NiO barrier layer by conventional one-step furnace decomposition of Ni(CH₃COO)₂·4H₂O, an additional step of high-pressure dehydration was introduced, avoiding the dehydration during the furnace reaction and, hence, significantly reducing cracks in the compact NiO film. Under simulated solar irradiation of 100 mW cm^–2 and with the as-prepared NiO barrier layer plus the optimal NiO photocathode, the P1 dye based dye-sensitized solar cell (p-DSSC) exhibits a J_SC of 3.05 mA cm^–2, a V_OC of 165 mV, and a power conversion efficiency of 0.16%, which is one of the most efficient p-DSSCs based on the P1 dye. Finally, a preliminary study on a tandem DSSC (t-DSSC) comprising an N719-sensitized TiO₂ photoanode and P1-adsorbed NiO photocathode was carried out. A V_OC of 700 mV was achieved, which is the sum of those in the two subcells, demonstrating the potential of electrophoretic preparation of NiO in a t-DSSC.