Poly(acrylonitrile)/activated carbon composite polymer gel electrolyte for high efficiency dye sensitized solar cells

In this article, we prepared poly(acrylonitrile)(PAN)/LiI/activated carbon (Ac. carbon) composite gel polymer electrolyte (GPE) and investigated its working mechanism in dye-sensitized solar cells (DSSCs) for the first time. The gel electrolyte, formed by a hot pressing method, is composed of poly(acrylonitrile) (PAN) as a gelling agent, ethylene carbonate (EC), propylene carbonate (PC), I2, 4-tert-butyl pyridine and 1-N-butyl-3-hexyl imidazolium iodide. We synthesised GPEs with the addition of different concentrations of Ac. carbon instead of the ceramic filler for application in DSSCs. The TiO2 photoelectrode films with 20 μm thicknesses were prepared by the hand spray technique. In addition, we also prepared PAN/SiO2 (∼20 nm) based gel electrolytes using the same procedure without Ac. carbon, and compared them to the optimal results. The GPEs were characterised by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical properties of the cells and the electrical conductivities of the GPEs were measured from the complex impedance plots. We found that the PAN/Ac. carbon GPE shows the best electrical conductivity of about 8.67 × 10−3 S cm−1. Cyclic voltammograms reveal that the PAN/Ac. carbon gel electrolyte itself has some catalytic behaviour, which may enhance its photovoltaic performance. Finally, we fabricated a DSSC based on this GPE and it exhibited the best solar cell efficiency of 8.42%, which is only 1% lower than that of a DSSC based on the conventional liquid electrolyte (9.5%).