Study of Polyaniline based Composites for Electrochemical Application

Abstract

An efficient, indium and iodine free, environment benign and cost effective dye sensitised solar cell (DSSC) is fabricated using novel combination of charge collectors, dye and electrolyte. The work reveals the selection of the charge collectors to be used for photoanode and counter electrode for DSSCs. The prepared cells utilised mixed polymer electrolyte, mixed natural dyes and innovative approach of using different glass substrates coated with two dissimilar (indium free) transparent conductive oxides (TCO), fluorine doped tin oxide (FTO) and aluminium doped zinc oxide (AZO) as current collectors for counter electrode and photoanode respectively. On an average 21.8% increased efficiency is attained by using different collectors for anode and for counter electrode. This justifies that DSSC based on FTO and AZO substrates displays better efficiency and hence suggested to be explored as an alternative to cost effective indium free system. Dyes used for the preparation were extracted from H. sabdariffa (A), B. vulgaris (B) and S. oleracea (C) and a cocktail dye (ABC) (by mixing three of the dyes) was also prepared. The N3 [Ru-(4, A'-dicarboxylic acid- 2, 2' - bipyridine)2(NCS)2] synthetic dye (taken for reference) based cell showed the highest efficiency of 6.19% out of all combinations prepared using varying sensitizers. The ABC dye happens to be the most sensitising dye of all the natural dyes with highest efficiency of 3.73%. A when blended with B, the efficiency has been increased by 110% and when blended with C it is increased by 85%. So green approach of blending natural dyes like chlorophyll dye with that of betalain and anthocyanin together resulted in an efficient DSSC. Similarly, to further optimise the polymeric electrolyte, polymer polyaniline (PANI) was doped with dopants like sulfamic acid (Elec@4), oxalic acid (Elec@5), titania (Elec@6), vanadium pentoxide (Elec@7) and ceric oxide (Elec@8). The efficiency of DSSC increased by atleast 11% when PANI was blended with acids and 28% increase when it is doped with metallic oxides. Moreover, Elec@7 has proved to be the promising polymeric composite to be used in DSSC (as an alternative to iodine free electrolyte) with highest efficiency of 3.62%. The cells were characterized by ultraviolet-visible (UV-vis), fourier transform infra-red (FTIR) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) , X- ray diffraction (XRD), thermogravimetric analysis (TGA), current- voltage (I-V) and incident photon conversion efficiency (IPCE) measurements. It can be hence represented as AZO/TiO2/ABC/Elec@7/Graphite/FTO.