Few-layer graphene supported polyaniline (PANI) film as a transparent counter electrode for dye-sensitized solar cells

Polyaniline (PANI) is an attractive alternative to platinum counter electrode for dye-sensitized solar cell (DSSC) due to its exceptionally low-cost. However, deposition of PANI film over FTO (Fluorine doped tin oxide) glass surface is very difficult. Here, we demonstrate a novel approach to grow PANI via in-situ polymerization on a porous few-layer graphene (FLG) support which has been prepared by simple solvent exfoliation method and deposited on FTO glass by tape casting. The existence of PANI on few-layer graphene is verified by scanning electron microscopy (SEM) images/energy-dispersive X-ray spectroscopy (EDX) mapping, Raman spectrum, Xray photoelectron spectroscopy (XPS). While, the presence of PANI in the form of emeraldine salt is confirmed by Fourier transformation infrared spectroscopy (FTIR) and UV-Vis absorbance spectroscopy. DSSC based on Gr/PANI and Pt counter electrode (CE) exhibited photoconversion efficiency (PCE) of 3.58% and 3.97% respectively, under one sun at 1 cm(2) active area. Electrochemical impedance spectroscopy (EIS) reveals that Gr/PANI based symmetrical cells exhibited higher double layer capacitance than Pt based symmetrical cells, believed to be attributed to higher catalytic active sites. However, Gr/PANI and Gr CEs displayed higher charge transfer resistance and Warburg impedance compared to Pt CE, resulting in superior PCE performance for Pt DSSC. Although the PCE of DSSC with Gr/PANI CE could not exceed the DSSC with Pt CE, but its optical properties and photovoltaic performance are comparatively good for consideration as the alternative.