Potentiodynamic Electrodeposition of CoSe2 Films and Their Excellent Electrocatalytic Activity as Counter Electrodes for Dye-Sensitized Solar Cells

Cobalt selenide (CoSe2) thin films are successfully formed on F-doped SnO2 (FTO) via a single step potentiodynamic electrodeposition process without any post treatment, and are utilized as counter electrodes (CEs) for dye-sensitized solar cells (DSSCs). The electrochemical behavior of the electrodeposited FTO/CoSe2 films is examined through Tafel polarization, cyclic voltammetry, and electrochemical impedance spectroscopy measurements. The results indicate that the FTO/CoSe2 films exhibit outstanding electrocatalytic ability and electrochemical stability toward the I-/I-3(-) redox couple. The optimized FTO/CoSe2 film fully covers the FTO substrate and features a nanoporous structure of interconnecting nanocrystalline networks, which is beneficial for the diffusion of ions and provides numerous electrochemical active sites. The optimized DSSC using FTO/CoSe2 as CE exhibits a significantly improved cell efficiency of 7.95% compared to that of the DSSC using FTO/Pt as CE (7.48%). (c) 2019 The Electrochemical Society.