High-performance and transparent counter electrodes based on polypyrrole and ferrous sulfide nanoparticles for dye-sensitized solar cells

The polypyrrole (PPy) electrode is synthesized by chemical oxidative polymerization on fluorine-doped tin oxide glass. Then the ferrous sulfide (FeS) nanoparticles is formed during the PPy nanoparticles by immersing the PPy electrodes in fresh Na₂S methanol solution (0.1 M) for 20 min. The synergistic effect of PPy and FeS nanoparticles make PPy/FeS CE possesses perfect transparency, good conductivity and excellent electrocatalytic activity for the reduction of triiodide/iodide. This would be attributed to improve the contact between counter electrode and electrolyte and enhance the collection and transmission of electrons. The transparent and high-efficiency PPy/FeS CE appears to be a potential candidate to the high cost and corrodible Pt CE of DSSCs. The dye-sensitized solar cells (DSSCs) based on PPy/FeS electrode can obtain a higher power conversion efficiency (PCE) of 7.48 % than that of DSSCs with pure PPy electrode (6.45 %) or Pt electrode (7.10 %) under full sunlight illumination (100 mW cm⁻², AM 1.5 G). Furthermore, the DSSC based on PPy/FeS electrode would obtain a high value of PCE (5.72 %) with back illumination.