Preparation Of Flexible Nanofibrous Films And Its Application In Dye-sensitized Solar Cells

As the third generation of new organic solar cell,the preparation process of dye-sensitized solar cell(Dye sensitized solar cells,DSSCs)is simple and low cost.It is an efficient and flexible environment-friendly device composed of photoanode,electrolyte and counter electrode(CE).The CE is an important part of the DSSCs which collects external circuit electrons and catalyze the reduction of triiodide.The common CE material is noble metal platinum(Pt),which has high efficiency but relatively high cost.Developing an inexpensive and efficient non-Pt CE material will further increase the efficiency of the DSSCs.In addition,the quality of the traditional glass based-DSSCs is heavy and fragile,which limits its application.The development of flexible DSSCs extends its application area,and improves the foundation for wearable solar cells.The highly flexible titanium carbide/carbon(TiC/C)nanofibrous films were prepared by electrospinning,stabilization,and carbonization.And the effects of the loading of TiC nanoparticles(TiC NPs)on the morphologies and flexural,electrical and electrochemical properties of TiC/carbon nanofibrous film were investigated.The FE-SEM,TEM,XRD,computer controlled stiffness tester and four-point probe tester were used to characterize the samples.The results showed that the TiC NPs were uniformly dispersed on the carbon nanofibers.With the increase of TiC NPs,the flexural property of TiC/carbon nanofibrous film increased.While,the electrical conductivity increased,reaching the largest value before decreasing as the amount of TiC NPs increased.It is likely that the precipitation of excessive TiC NPs increased the defect structures of the TiC/carbon nanofibrous film,the contact resistance between the nanofibers gets larger and the conductivity of the composite nanofibrous membrane became poor.The highly flexible films showed promising electrical conductivity and electro-catalytic activity.Hence,they were employed as counter electrodes(CEs)for flexible dye-sensitized solar cell(Flexible DSSCs,FDSSCs).After optimization of the amount of TiC NPs in carbon nanofibers(when the Tip content in precursor was 12 wt%),a high conversion efficiency(?)of 3.80%was obtained.Based on the optimum amount of TiC NPs,the mesopores TiC/carbon nanofibrous films were fabricated by the introduction of various amount of PMMA in electrospun solution.The FE-SEM,TEM,nitrogen adsorption/desorption isotherms,computer controlled stiffness tester and four-point probe tester were used to characterize the samples.With the ratio of PMMA:(PAN/PVP)increasing,the specific surface area of mesoporous TiC/carbon nanofibrous membranes increased from 228 m2 g-1 to 280 m2 g-1,and the average conductivity increased from 33.33 S m-1 to 80.00 S m-1 corresponding to 1:1.With the ratio of PMMA to(PAN/PVP)being further increased,the specific surface area of the composite nanofibers films was almost constant while the conductivity decreased.The increased surface area and conductivity facilitated the diffusion of electrolyte and reduction of triiodide,resulting in the improvement of the properties of CEs.When the FDSSCs were assembled with mesoporous TiC/carbon nanofibrous films as CEs,the ? can be further enhanced up to 4.47%.Based on the optimal mesopores structure,the molybdenum disulfide(MoS2)/TiC/carbon nanofibrous film was prepared by pyrolysising of the MoS3 obtained by the solution method and the mesoporous TiC/carbon nanofibrous film.The FE-SEM,TEM,XRD and XPS were used to characterize the samples.MoS2 was embedded in the surface of the TiC/carbon nanofibrous film with particles and burrs,and a small amount of MoS2 was oxidized to MoO3 in air.The addition of non-conductive MoS2 and MoO3 increased the resistance of the CE slightly,but it had little effection on the flexibility and electrochemical properties of the nanofibers film.It was still suitable for the CE of FDSSCs.When the FDSSCs was assembled with MoS2/TiC/carbon nanofibrous film as CE,the ? can be further enhanced up to 5.08%.And comparing to that of FDSSCs with mesoporous TiC/carbon nanofibrous film CE,? have improved by 13.6%,which can be even comparable to the Pt/FTO CE(4.60%).