Energy Band Transition and Voltage Compensation via Surface Stoichiometry Alteration in p-Type Dye-Sensitized Solar Cells

To fundamentally ameliorate the photovoltaic performances of dye-sensitized solar cells (DSSCs), p-type DSSCs (p-DSSCs) have attracted considerable attention over the last two decades. Herein, by means of a modification with a Ni(NO3)2 aqueous solution, the stoichiometry of Ni atoms on the surface of a NiO electrode markedly increased. As a result of the change in donor ability and built-in electric field, the quasi-Fermi level and the valence band of the semiconductor were greatly reduced, thus effectively improving the open-circuit voltage of the NiO-film-based photovoltaic device. In addition, the increased short-circuit current density was attributed to the change of the surface distribution state of the sensitizer. Consequently, the power conversion efficiency of the photovoltaic device based on the Ni-salt-modified electrode increased by 35.7% from 0.14 to 0.19% compared to that of the plain electrode. This method opens a new strategy to improve the photovoltaic efficiencies of p-DSSCs.