A high performance Pt-free counter electrode of nickel sulfide/multi-wall carbon nanotube/titanium used in dye-sensitized solar cells

Abstract

Multi-wall carbon nanotubes (MWCNTs) were deposited on a titanium (Ti) foil substrate by using electrophoresis, then a nano-corallines nickel sulfide (NiS) was deposited on the MWCNTs by using a pulse potentiostatic method. The high performance NiS/MWCNT/Ti hybrid film was firstly used as a Pt-free counter electrode (CE) in dye-sensitized solar cells (DSSCs). The surface of MWCNTs was wrapped with a nano-corallines NiS thin film of ∼45 nm in thickness. Under full sunlight illumination (100 mW cm−2, AM 1.5 G), DSSCs with a NiS/MWCNT/Ti CE achieved an enhanced photovoltaic conversion efficiency of 7.90%, while DSSCs with a Pt/Ti CE obtained the efficiency of 6.36%. The characterization of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) indicated that nano-corallines NiS had high electrocatalytic activity for I3− reduction, MWCNTs had high specific surface area and low resistance, and the synergistic effect of NiS and MWCNTs endowed the superior features of the hybrid film. Therefore, the NiS/MWCNT/Ti CE can be used as a promising alternative CE in low-cost and large-scale DSSCs.