Synthesis And Properties Of Nanofibrous Membrane For Dye-sensitized Solar Cells

The FTO/titania nanoparticles/titania nanofibrous membrane as an electode fordye-sensitized solar cells （DSSC） has been fabricated. The TiO₂nanoparticles film withthickness of3.0μm was spin-coated onto the fluorine doped tin oxide （FTO） conducting glassprior to electrospining by use the concentrated precursor solution to improve the bond strength.The TiO₂nanofiers were fabricated by eletrospun titanium （IV） isopropoxide/polyvinyl acetate（TiP/PVAc） fibers and subsequent calcination in high temperature. The TGA, FE-SEM, XRD,FT-IR, and TEM were used to characterize the samples. After calcinations for30min at500°C,the obtained nanoparticles have a size of ca.70nm, and the obtained nanofibers have an averagediameter of ca.97±30nm, which are composed of pure anatase TiO₂phase. The thickness ofnanofibous membrance was about3.0μm. The DSSC with an area of⁰.3cm²under standard testconditions （100mW·cm-2,25°C and AM1.5G） showed open-circuit voltagee （Voc）, short-circuitcurrent （Jsc）, Fill Factor （FF）, incident photon-to-current conversion efficiency （IPCE）, andenergy conversion efficency （η） are0.700V,10.6mA/cm²,60.2%,42.1%, and4.47%,respectively, and η has improved by14.0%comparing to that of DSSC containing a TiO₂nanoparticles membrane.Hydrochloric acid （HCl） treatment of TiO₂nanofibrous membrane, Zn²⁺doped TiO₂nanofibers, and ZnO coating TiO₂nanofibers by coaxial electrospining were employed toimprove the performance of DSSC with nanofibrous membrane.The influence of hydrochloric acid treatment of TiO₂nanofibers on performance showed Jsc,Voc, FF, IPCE, and η increased with increasing the concentration of hydrochloric acid, reached amaximum value and afterwards decreased. With the concentration of HCl of0.1M, Voc and FFreached maximum values of0.720V and60.9%, respectively. With the concentration of HCl of0.05M, Jsc, IPCE at wavelength of350nm, and η have maximum vaules of11.1mA/cm²,46.3%,and4.75%, respectively. And comparing to that of DSSC with TiO₂nanofbrous electrodewithout acid treatment, η have improved by6.26%.Zn²⁺doped TiO₂nanofibers were prepared by electrospinning followed by calcination. TGA, FE-SEM, XRD, and FT-IR were used to characterize the fibers. The obtained Zn²⁺doped TiO₂nanofibers have a little smaller than that of TiO₂nanofibers in diameter and are composed ofanatase TiO₂phase with the slight elongation of lattice parameters in ‘c’ axis while the other axisremained constant comparing to the pure TiO₂. With the doping content of Zn²⁺increasing from0to5at%, the dye adsorbed by the nanofibrous increased. And Jsc, Voc, FF, IPCE, and η ofDSSC fabricated with Zn²⁺doped TiO₂nanofibours membrane increased with increasing thecontent of Zn²⁺, reached a maximum value and afterwards decreased. The maximum vaules ofJsc, Voc, FF, IPCE, and η are, respectively,0.734V,11.1mA/cm²,60.3%,46.3%, and4.91%withthe doping content of Zn²⁺of0.5%and an enhancement of9.84%relative to η of a cellcontaining a TiO₂nanofibrous membrane.The core-shell structured TiO₂-ZnO nanofibers were fabricated on FTO conducting glasssubstrate by coaxial electrospinning and calcination at500°C. To enhance interfacial adhesion ofcore-shell structured TiO₂-ZnO nanofibers between FTO, a thin composite TiO₂/ZnOnanoparticles film was pre-deposited on FTO conducting glass by spin-coating as the above.FE-SEM, TEM, FT-IR, XRD, XPS were used to characterize the fibers. The results showedcore-shell structured TiO₂-ZnO nanofibers had an average diameter of ca.170nm and werecomposed of shell of ca.35nm thick wurtzite ZnO and core filled with ca.100nm thick anataseTiO₂fibers. The DSSC with core-shell structured ZnO-TiO₂nanofibrous membrane electrodeshowed Jsc of11.3mA·cm^-2, Voc of0.745V, FF of61.2%, IPCE of47.1%, and η of5.15%, withan enhancement of15.2%, relative to η of a cell containing a TiO₂nanofibrous membrane.The better photoperformances of DSSC fabricated by core-shell structured ZnO-TiO₂nanofibous membrane electrode than those of the others.