H3PW12O40/Co3O4–Cu2S as a low-cost counter electrode catalyst for quantum dot-sensitized solar cells

This paper reports for the first time the preparation of Co3O4 nanorods by simple hydrothermal and annealing methods, which are doped with polyoxometalates that act as an intermediary in electronic transmission to accelerate electron transport. The designed H3PW12O40(PW12)/Co3O4–Cu2S composite film was prepared by the screen printing method to boost its efficiency as the counter electrode for quantum dot-sensitized solar cells, where the preparation process is simple and inexpensive. PW12/Co3O4–Cu2S (Jsc = 16.60 mA cm−2, Voc = 0.636 V, Rct = 0.32 Ω and FF = 0.436) shows better electrocatalytic performance compared to the original Co3O4 and Cu2S. Accordingly, the photoelectric conversion efficiency of PW12/Co3O4–Cu2S is 4.67%, which is 10%, 46%, 55.6%, and 72% higher than those of Co3O4–Cu2S (4.2%), Cu2S (2.54%), PW12/Co3O4 (2.07%), and Co3O4 (1.30%), respectively. Electrochemical impedance spectroscopy and Tafel measurements performed on two CE symmetric virtual cells proved the excellent electrocatalytic activity of PW12/Co3O4–Cu2S. Therefore, this composite film can be used as an alternative option for QDSSC counter electrodes.