Dye-sensitized solar cell based on poly(ε-caprolactone) gel polymer electrolyte and cobalt selenide counter electrode

In this work, gel-like polymer electrolytes were prepared by incorporating poly(epsilon-caprolactone) (PCL) into dimethylformamide (DMF)-potassium iodide (KI) liquid electrolytes. The optimized gel polymer electrolyte has the composition of 40 wt.% of PCL, 45 wt.% of DMF and 15 wt.% of KI with a conductivity of 2.72 x 10(-3) S cm(-1) at room temperature. Increase in conductivity with temperature is attributed to the increase in diffusion coefficient, D, number, n and mobility, mu of ions as determined from Nyquist plots fitting. Cobalt selenide (CoSe) was prepared by hydrothermal method and used as counter electrode catalysts in dye-sensitized solar cells (DSSCs). X-ray diffraction (XRD) studies show the formation of the as-prepared CoSe. The morphology and stoichiometric composition of CoSe were studied by field-emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDX). The PCL-DMF-KI gel polymer electrolytes were assembled into DSSCs with CoSe or platinum (Pt) as the counter electrodes. DSSC with CoSe counter electrode shows an efficiency of 6.74% while DSSC with Pt counter electrode yields an efficiency of 6.99%. Impedance studies of DSSCs suggest that the electrocatalytic reduction of triiodide, I-3(-) by the CoSe is as good as Pt.