Application Of Electrospinning In Counter Electrodes Of Dye-sensitized Solar Cells

As a third-generation solar cell,dye-sensitized solar cells are expected to successfully replace silicon solar cells due to their simple preparation method,low cost and flexibility and flexibility.At present,the counter electrode of dye-sensitized solar cell generally adopts noble metal platinum.Although platinum has excellent electron conductivity and electrocatalytic ability,its low storage,high price,and easy corrosion by electrolytes have seriously hindered the development of dye-sensitized solar cells.In this study,carbon fiber doped with a metal catalyst was prepared by a flexible and simple electrospinning technique,which was applied to the counter electrode;and the metal organic framework material was first applied to the study of the counter electrode.The following are the main contents of this study:Firstly,the optimum parameters of electrospun carbon fibers with polyacrylonitrile as precursor and N,N-dimethylformamide as solvent were explored through orthogonal experiments of four factors(positive high pressure,negative high pressure,distance,propulsion speed)and three levels.After pre-oxidation and carbonization in a vacuum tube furnace,the best parameters were positive high pressure 17 kV,negative high pressure 2 kV,distance 12 cm,and propulsion speed 0.2 mL·h-1 after observation by scanning electron microscope.The fibers obtained under these conditions have the finest diameter and the most uniform distribution,which facilitates electron transport,adsorption of the catalyst,and penetration of the electrolyte.Subsequently,the main testing methods in physical structure,chemical composition,electrochemical characterization test and photoelectric conversion efficiency in the research field of dye-sensitized solar cell counter electrode were statistically analyzed and laid a foundation for subsequent research.Next,cobalt acetate and ferric nitrate were added as a precursor of the bimetallic catalyst to the solution,and the carbon nanofibers containing the iron-cobalt alloy were obtained by using the optimum spinning parameters obtained above.The XRD,Raman and XPS test analysis sho,ws that the iron-cobalt element is successfully doped into the carbon fiber and has a good crystal structure;It can be observed by SEM(EDX),TEM(HR-TEM,EDS)test that the fiber has good morphology,iron and cobalt elements are evenly distributed on the fiber surface,and carbon fiber and iron cobalt have obvious lattice fringes;Electrochemical testing methods EIS and CV analysis show that iron-cobalt carbon nanofibers have lower total series resistance and charge transfer resistance,indicating that electrons have excellent transmission kinetics,larger redox reaction area and lower peak-peak separation potential,showing more efficient electrocatalytic ability;The photoelectric conversion efficiency(J-V)test showed that the efficiency of the iron-cobalt carbon nanofiber counter electrode reached 98.5%of the efficiency of the platinum counter electrode;The endurance test of the electrode showed that the iron-cobalt carbon nanofiber showed a smaller peak current density attenuation and a stronger corrosion resistance to the electrolyte in the CV test of 100 cycles.In general,iron-cobalt carbon nanofibers are expected to be a powerful alternative to platinum counter electrode.The Co-ZIF and Co-ZIF/GO counter electrodes were successfully prepared by hydrothermal synthesis.The XRD,XPS and SEM tests showed that the Co-ZIF/GO electrode material has excellent crystal structure and hexagonal shape Co-ZIF has been successfully grown on graphene sheets,and the material has high purity.The mixed valence element composition is also beneficial to accelerate the reaction.Electrochemical performance analysis of CV and EIS showed that the Co-ZIF/GO electrode material has lower reduction peak current density and peak-to-peak separation potential,indicating that the material has better ion reaction kinetics in the battery reaction;100 cycles The durability test of CV shows that the Co-ZIF/GO counter electrode has better corrosion resistance and stability relative to the Pt electrode in the iodide electrolyte system.The AC impedance spectrum shows that the Co-ZIF/GO counter electrode has a lower series resistance,indicating that the electron has good transmission kinetics.The photoelectric conversion efficiency test of the assembled battery was carried out.The results show that the photoelectric parameters of the Co-ZIF/GO counter electrode battery are:open circuit voltage 0.65 V,short circuit current 15.35 mA·cm-2,fill factor 0.43,photoelectric conversion efficiency 3.89%is 98%of the platinum counter electrode battery under the same preparation conditions.In this paper,electrospinning nanofibers and metal-organic frameworks are effectively applied to DSSCs electrodes,and the efficiency parameters are almost the same as those of current standard Pt electrodes.The problems of high cost and poor stability of Pt electrodes are effectively solved,and the practical application and commercial development of DSSCs are promoted.