Composite Counter Electrode Materials Based On Carbon Nanofibers For Efficiency Dye-Sensitized Solar Cell

As a third-generation solar cell,dye-sensitized solar cell?DSC?has attracted much attention due to its low cost of production,high power conversion efficiency,simple production procedure,and environmental friendliness.Generally,a DSC comprises three components,a photoanode?a mesoporous semiconductor oxide film that absorbed a dye?,a CE,and an electrolyte.TiO₂ is widely used as the semiconductor;N719 is used as the dye;the electrolyte commonly contains I3-/I-redox couples.Pt is generally used as the CE catalytic material.However,Pt is an expensive noble metal with limited reserves.Moreover,Pt can be corroded in I3-/I-electrolyte,influencing the stability of the DSC.Therefore,it is imperative to develop Pt–free catalytic materials that show the merits of low cost,high activity,and strong erosion resistance to cut down the DSC cost as well as to improve its stability.In recent years,composite materials have attracted considerable attentions,because they are expected to replace the noble metal?Pt?in the fields of energy conversion,energy storage,and organic synthesis.Building on the current research on the composite catalytic materials,this research designed and synthesized a class of composite catalytic materials based on carbon nanofibers,containing sulfides,alloy and oxides.Then the prepared composite catalytic materials were used as low cost counter electrodes?CEs?in DSC to fabricate photovoltaic devices and high power conversion efficiencies were obtained.First,electrospun carbon nanofibers?ECs?were synthesized and used as supporter.Co3S4 nanospheres were synthesized by hydrothermal synthesis method and loaded on the surface of ECs to fabricate the composite material of Co3S4/ECs.Combining ball-milling and spray methods,Co3S4/ECs were prepared as counter electrode?CE?for DSC to research the photoelectric property.The results showed that in Co3+/Co2+ electrolyte system,Co3S4/ECs composite obtained superior photoelectric property,higher than Pt,which demonstrated the preparation of composite materials based on electrospun carbon nanofibers was feasible.Second,Pt₃ Ni alloy was synthesized by solvothermal method and loaded on the surface of carbon nanofibers?CNs?to fabricate the composite material of Pt₃Ni/CNs.In order to improve the photoelectric property of Pt₃Ni/CNs,transition metal Cr was doped in Pt₃ Ni alloy to fabricate the composite material of Cr-Pt₃Ni/CNs.The same method was used to prepare the CEs for DSC to research the photoelectric property.The results showed that in I3-/I-electrolyte system,Pt₃Ni/CNs composite achieved a superior power conversion efficiency?PCE?of 8.34%,higher than that of Pt?7.04%?.Meanwhile,an improved PCE was obtained by Cr-Pt₃Ni/CNs composite.All the results showed that the preparation of composite materials based on electrospun carbon nanofibers was an effective method to fabricate the high efficiency and low cost CE.Besides,the doping of transition metal Cr was in favor of improving the photoelectric property.Finally,MnO₂ was synthesized by hydrothermal synthesis method and coated on the surface of carbon nanofibers?CNFs?to fabricate the composite material?MnO₂/CNFs?.Four composites with different thickness of MnO₂ coated on the surface of CNFs were prepared to research the photoelectric property affected by the different thickness of MnO₂ nanorods.It was found that the composites of MnO₂/CNFs achieved the highest catalytic activity when the thickness of MnO₂ was nearly 100 nm,and the DSC used it as counter electrode showed a high PCE of 8.86%,higher than the Pt CE based DSC?8.27%?.In a word,a series of low cost composite materials based on carbon nanofibers with high efficiency were designed and synthesized for the DSC.As a result,the composite materials performed better than Pt,which greatly expand the range of CE catalytic materials.By contributing to the reduction of the cost of production for DSC,this research improves the competitiveness of DSC in photovoltaic field.