Controllable growth of NixCoySe films and the influence of composition on the photovoltaic performance of quasi-solid-state dye-sensitized solar cells

Abstract

Herein, ternary nickel cobalt selenide (Ni_xCo_ySe) films with controllable stoichiometric ratios were prepared in situ on a conductive substrate. When the total amounts of metal salts and selenium are kept constant, the stoichiometric ratio of Ni_xCo_ySe nanoparticles in situ growing on the conductive substrate can be controlled by adjusting the feed ratios of metal salts in the reaction solution. When the in situ-grown Ni_xCo_ySe films are directly used as counter electrodes of quasi-solid-state dye-sensitized solar cells (QSDSSCs), the electrocatalytic properties of Ni_xCo_ySe and the corresponding photovoltaic performances depend on the Ni/Co molar ratio. The QSDSSC device with the Ni_0.12Co_0.80Se counter electrode achieves the best power conversion efficiency of 8.61% among those with the counter electrode at other stoichiometric ratios. Impressively, the ternary Ni_0.12Co_0.80Se is superior to the binary selenides and the Pt control in terms of both electrocatalytic activity and solar cell performance; this is attributed to the synergetic effect between nickel and cobalt atoms in the ternary compound.