Non-covalent construction of non-Pt counter electrodes for high performance dye-sensitized solar cells

Abstract

Non-covalent bonds (π–π stacking, electrostatic forces and van der Waals interactions) have been constructed between multi-walled carbon nanotubes (MWCNTs) and poly(diallyldimethylammonium chloride) (PDDA). The non-Pt based counter electrodes (CEs) for the dye-sensitized solar cells (DSSCs) have been fabricated by spin-coating the aqueous dispersions of PDDA/MWCNTs on the Fluorine-doped SnO2 (FTO) substrates. Due to the presence of the linker PDDA, the MWCNTs show enhanced dispersibility and long-termed stability in aqueous solution which improves the cohesiveness on the FTO. The optimum dosage of PDDA for a stable dispersion is found at the mass percentage of ~15.0 % (PDDA/MWCNTs), and the zeta potential of the final composite PDDA/MWCNTs is about 27.0 mV as measured in neutral water solution (pH = 6.8). The prepared PDDA/MWCNTs CEs exhibit low charge-transfer resistance (Rct = 4.6 Ω cm−2) and high electrocatalytic efficiency, which was confirmed by the electrochemical impedance spectroscopy and cyclic voltammetry. The photoelectric conversion efficiency (η) of the DSSCs fabricated with PDDA/MWCNTs is 5.66 %, which is greater than that (η = 4.48 %) of the pristine MWCNTs. This data is comparable to that of the conventional platinum coated CEs (η = 6.73 %). Non-covalent bonds have been constructed between multi-walled carbon nanotubes and poly(diallyldimethylammonium chloride), and a type of non-Pt based counter electrodes for high performance dye-sensitized solar cells were fabricated.