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Nickel cobalt sulfides (Ni-Co-S) have been extensive developed as platinum-free counter electrode (CE) materials for dye-sensitized solar cells (DSCs). However, the power conversion efficiency (PCE) of DSCs with Ni-Co-S CEs needs to be further improved by changing crystalline structure of Ni-Co-S. Herein, Ni-Co-S with amorphous structure have been synthesized on fluorine-doped tin oxide (FTO) glass by a potential reversal electrodeposition technique. The morphology of Ni-Co-S films can be controlled through adjusting the molar ratio of Ni and Co ions in the electroplating solution. Ni-Co-S films can be directly applied as low-cost CEs of DSCs. The results demonstrate that Ni-Co-S CEs exhibit excellent electrocatalytic performance for I3− reduction, owing to the synergistic effect and amorphous structure of Ni-Co-S films. Particularly, the DSC based on Ni-Co-S CE with the optimized Ni/Co ratio has achieved the high PCE of 8.18%, which is larger than that of the DSC with platinum (Pt) CE (6.33%).