The effect of transition metal ions (M^(2+)=Mn^(2+),Ni^(2+),Co^(2+),Cu^(2+)) on the chemical synthesis polyaniline as counter electrodes in dye-sensitized solar cells

The effect of transition metal ions(M^(2+)=Mn^(2+),Ni^(2+),Co^(2+),Cu^(2+)) on the chemical synthesis of polyaniline(PANI) used as a platinum-free counter electrode(CE) in dye-sensitized solar cells(DSSCs) was investigated.PANI was synthesized by co-polymerization of aniline in the presence of different transition metal ions by using potassium dichromate in acidic medium. It was found that the ion doping of PANI showed a certain catalytic activity for the regeneration of traditional iodide/triiodide(I^-/I_3^-) redox couples. The power conversion efficiency(η) of PANI CEs doped with Mn^(2+),Ni^(2+),Co^(2+) (4.41%, 2.36% and 2.10%, respectively) were higher than 1.94%, the value measured for PANI CE without doping. Doping with Cu^(2+)decreased the power conversion efficiency of PANI CE(PANI-Cu^(2+) η = 1.41%). The electrical properties of the PANI, PANI-Ni^(2+), PANI-Co^(2+),PANI-Mn^(2+) and PANI-Cu^(2+) were studied by cyclic voltammetry(CV), impedance(EIS), and Tafel polarization curve. The experimental results confirmed that PANI was affected by the doping of different transition metal ions(M^(2+)=Mn^(2+),Ni^(2+),Co^(2+),Cu^(2+)). These results indicate a potential application of ion doped PANI as counter electrode in cost-effective DSSCs.

Synthesis of La_2MoO_6@MWCNTs composite catalysts as Pt-free counter electrodes for dye-sensitized solar cell

Pt-free counter electrode(CE) composed of La2 MoO(LaO-MoO) was successfully synthesized by simple pyrolysis of lanthanum acetate(CHOLa·xHO) and hexaammonium heptamolybdate tetrahydrate((NH4)6 MoO·4 HO). Furthermore,three proportions composites catalysts of La2 MoO@MWCNTs based on La2 MoOand multiwall carbon nanotubes(MWCNTs) were prepared and characterized as Ptfree catalyst for CE in dye-sensitized solar cells(DSSCs). The morphology and structure of La2 MoO@MWCNTs composites were determined by scanning electron microscopy, transmission electron microscope and X-ray diffraction. The electrochemical performance of La2 MoO@MWCNTs composite catalysts for CEs was determined by photocurrent-voltage measurements, cyclic voltammetry,electrochemical impedance spectroscopy, and Tafel polarization. The power conversion efficiencies of4.68%, 4.87% and 5.06% are obtained for La2 MoO:MWCNTs with the mass ratios of 5:1, 3:1 and 1:1 towards the reduction of I~-to I~-under the same conditions,respectively,which are superior to those of MWCNTs(3,94%) and La2 MoO(1.71%) electrodes. The experimental results reveal that the presence of MWCNTs results in an augmented active catalytic surface area and enhanced charge transfer from CE to the electrolyte.