Ternary metal selenide/PEDOT composite as a durable catalyst for I-/I3- regeneration in dye-sensitized solar cells

Abstract

Corrosion resistant, strongly adhering, and efficient catalysts are important for long-term operation of dye-sensitized solar cells (DSSCs). Poly (3,4-ethylenedioxythiophene), PEDOT, has desirable electrical and corrosion resistant properties in catalysis, but poor adhesion onto most conductive substrates. Platinum also presents cost and sustainability problems, despite its good performance. To realize a synergistic combination of all properties of an effective catalyst, we have developed a composite comprised of a highly redox active and strongly adhering ternary metal selenide (FeNiCoSe) whose long-term operational stability in iodide/triiodide (I-/I<inf>3</inf>-) regeneration is ensured by a protective layer of PEDOT. This composite exists as an inter-twinned material, enabled by the two-step electrodeposition approach employed at room temperature. It combines the mechanical durability of FeNiCoSe with the chemical stability of PEDOT. Electrochemical tests in I-/I<inf>3</inf>- solution revealed negligible degradation (ΔE<inf>pp</inf> = 1 mV; ΔJ<inf>red</inf> = -0.036 mA cm-2) of the composite as a counter electrode material after 100 cyclic voltammetry scans. DSSCs with this composite exhibited a power conversion efficiency of 8.81 %, exceeding reference devices based on pure PEDOT (8.29 %), FeNiCoSe (8.44 %), and Pt (8.22 %). Long-term testing confirmed durability as the device retained 84.41 % of its initial efficiency after 3 months, versus 78.24 % for Pt, and 77.24 % for PEDOT, while FeNiCoSe degraded completely. These results demonstrate the advantages of composites with tailored needs in catalytic applications. © © 2025. Published by Elsevier Ltd.