A composite film of TiS2/PEDOT:PSS as the electrocatalyst for the counter electrode in dye-sensitized solar cells

Abstract

A composite film of titanium disulfide/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (TiS₂/PEDOT:PSS) was deposited on a indium-doped tin oxide (ITO) conducting substrate by the drop coating technique, as the counter electrode (CE) of dye-sensitized solar cells (DSSCs). TiS₂ particles were well distributed in the polymer matrix of PEDOT:PSS and served as an electrocatalyst material for the redox reaction of iodide/triiodide ions (I⁻/I₃⁻) with high conductivity and attractive catalytic ability. The TiS₂/PEDOT:PSS composite CE showed good uniformity and provided a large electrochemical surface area, which resulted in a high cell efficiency (η) of 7.04%. The high efficiency of the cell with the TiS₂/PEDOT:PSS composite CE could be a potential choice for replacing the expensive Pt CE. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and energy dispersive X-ray spectroscopy (EDX) were used to characterize the morphology of different CEs, including Pt, bare TiS₂, bare PEDOT:PSS and the TiS₂/PEDOT:PSS composite. The catalytic ability and electrochemical properties of the CEs were quantified by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), Tafel plots and rotating disk electrode (RDE) measurements. The high cell efficiency of DSSCs with the TiS₂/PEDOT:PSS composite CE was verified by the incident photon-to-current conversion efficiency (IPCE) curves.