FeS counter electrode (CE) with the structure of three-dimensional nanospheres for quantum dots-sensitized solar cells (QDSCs) is first fabricated by alternating current (AC) etching the A3 carbon steel and characterized with scanning electron microscope (SEM), Transmission electron microscope (TEM), current voltage and impedance spectroscopy. The device applying FeS CE achieves a power conversion efficiency of 3.34%, which are much higher than that of using Pt (1.01%) and conventional Cu2S (1.54%). These results indicated that AC provides an efficient, simple and cost-effective method to fabricate CE for QDSCs. (C) 2014 Elsevier B.V. All rights reserved.