Abstract
Two quaternary chalcogenides of ThCr2Si2-type K2FeCu3Q4 (Q for S and Se) were utilized as new type of Pt-free counter electrodes (CEs) for dye-sensitized solar cells (DSSCs). The X-ray photoelectron spectroscopy (XPS), Mott−Schottky analysis, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were performed to clarify the differences in energy band alignments, electrocatalytic and photovoltaic performances. A photoelectric conversion efficiency (PCE) of 5.07% was achieved in DSSCs assembled with K2FeCu3Se4 CE, which was obviously superior to that of K2FeCu3S4 CE (3.42%) and comparable with that of Pt CE (6.25%) under one sun AM 1.5 G illumination (100 mW cm−2). Compared to K2FeCu3S4 CE, the higher PCE of K2FeCu3Se4 CE can be attributed to the better catalytic activity for I3− reduction, stronger driving force for electron injection from CE to electrolyte, faster electron transfer and electrolyte diffusion channels.
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