Nanoparticles Modified By Functionalized Multiwall Carbon Nanotubes As Counter Electrodes(CEs)in Dye-sensitized Solar Cells(DSSCs)

In the global environment and economy,the development of renewable alternatives to current methods of power generation is extremely worthwhile for sustainable development.The clean solar energy converted directly to electricity offers an ideal solution for photovoltaic(PV)systems.Nevertheless,silicon-based photovoltaic(PV)devices are prevented,despite their higher efficiency,by their high production costs and uncompetitive yields in comparison to conventional methods.Therefore,exploring non-silicon alternatives has taken on considerable momentum,with improved economic effective,practical,and sustainable results both in academia and the industry in the last two decades.Favorable photovoltaic systems have been thoroughly investigated including all-polymer,tiny molecules,poly-inorganic-nanoparticle hybrid,and dye-sensitized solar cells(DSSCs).In recent years,the dye-sensitized solar cells(DSSCs)have attracted extensive academic and industrial attention because of their low price,easy manufacturing,and excellent performance.An important component of the DSSC is the counter-electrode(CE).The cost and efficiency of cells are affected directly by their prices and quality.Noble metal platinum is traditionally used as CE.The platinum electrode offers high electrocatalytic efficiency,superior conductivity,and chemical stability for I ₃^-reduction.Nevertheless,large-scale DSSC production can be impeded by rare storage and high platinum cost.Therefore,for the industrialization of(DSSCs),the exploration of non-Pt and effective electrode materials is important.This dissertation will focus on the development of several efficient,non-Pt electrode materials and the analysis of their electrocatalytic properties.The synthesis and application of metal oxides and sulfides as counter electrodes in the DSSC has been reported in previous research.The corresponding PCEs of DSSCs are undesirable as a result of the weak conductivity and catalytic activity of a single material.The main purpose of the work is to achieve the electrode materials for DSSCs with high catalytic efficiency.The key materials in this research,including the Co₃O₄,SnO₂,SnS₂,and Zn S compounds,were modified by adding carbon nanotubes,reduced graphene oxide,and nitrogen doping reduced graphene oxide.The dissertation then used conventional methods to create DSSC counter-electrodes and studied its optical and electrical characteristics.The content is as follows:(1)Platinum-free and novel hybrid counter electrode is an important part of dye-sensitized solar cells(DSSCs).More and more researches reported that transitional metal oxide nanoparticles could be used as CEs in DSSCs.However,they are ready to be corroded by electrolyte,leading to worse stability in catalytic activities for triiodide reduction in the cyclic voltammetry(CV)test.Multiwall carbon nanotubes(MWCNTs)have a tangled network,exceptional specific surface area,and unique hollow composition that can be higher for use as a CE material.The electrochemical performance analysis indicates that the Co₃O₄nanoflakes and functionalized multiwall carbon nanotubes(f-MWCNTs),wrapped with N-doped reduced graphene oxide(Co₃O₄@f-MWCNTs@N-RGO)electrode has lower charge transfer resistance(R_ct)on the electrolyte/electrode interface and higher catalytic ability than bare Co₃O₄nanoflakes.Power conversion efficiency(PCE)of the prepared hybrid has been achieved up to 8.42%,in contrast to the platinum-based counter electrode(PCE=7.81%)used in DSSCs.Besides,Co₃O₄@f-MWCNTs with N-RGO hybrid material shows strong catalytic activities for triiodide reduction,superior to Co₃O₄ nanoflakes in the CV test.(2)In this research,SnO₂@SWCNTs@RGO based nanocomposite was synthesized by a one-step hydrothermal method and reported a new cost-effective platinum-free counter-electrodes(CEs)in dye-sensitized solar cells(DSSCs).The CEs were formed by using the nanocomposites with the help of a pipette using a doctor blade technique.The efficiency of this nanocomposite revealed significant electrocatalytic properties upon falling the triiodide,possessing to the synergistic effect of SnO₂nanoparticles and improved conductivity when SWCNTs dispersed on a graphene sheet.SnO₂@SWCNTs@RGO nanocomposite CEs give more stable catalytic activities for triiodide reduction than SnO₂ and SWCNTs CEs in the cyclic voltammetry(CV)analysis.Furthermore,to the subsistence of graphene oxide,the nanocomposite acquired both higher stability and efficiency in the nanocomposite.(3)SnS₂ nanoflakes are easy to agglomerate,causing a failure of the electrocatalytic performance in connection with electrolytes and nanoflakes.Therefore,the counter electrodes were fabricated using SnS₂ nanoflakes moored on functionalized multiwall carbon nanotubes(f-MWCNTs)and the reduced graphene oxide(RGO)by hydrothermal method.The efficiency of SnS₂@f-MWCNTs@RGO nanohybrid revealed significant electrocatalytic activity for the reduction of triiodide.Outstanding chemical stability corresponds to the synergistic effects of SnS₂(NFs)anchored on f-MWCNTs invested high conductivity of RGO.Furthermore,SnS₂@f-MWCNTs@RGO nanocomposite as a counter electrode in DSSCs showed a startling efficiency of 8.7%for triiodide/iodide redox couple.It's expected that the present novel form of electrode fabrication provides new horizons of research in the field of energy-based applications.(4)Here,we report a zinc sulfide quantum dots Zn S(QDs)moored N-doped functionalized carbon nanotubes wrapped with reduced graphene oxide(r GO).The multiwall carbon nanotubes(MWCNTs)have a tangled network,a particular surface area,and a distinctive hollow structure may be greater for use as CE material.Zn S@N.f-MWCNTs@r GO composite as the counter electrode(CE)on fluorine-doped tin oxide substrates in dye-sensitized solar cells(DSSCs)fabricated using doctor blade technique.The electrochemical performance showed that on the electrolyte/CE interface the Zn S(QDs)and N-doped f-MWCNTs wrapped with r GO Zn S@N.f-MWCNTs@r GO the electrode has lower transfer charge resistance(R_ct)and greater catalytic capacity than naked Zn S(QDs).Power conversion efficiency(PCE)of 9.4%was attained for this DSSCs gadget which is higher than that of DSSCs gadget utilizing Zn S(QDs),Zn S@N.f-MWCNTs,Zn S@r GO and Pt.Also,the DSSC device fill factor(FF)using Zn S@N.f-MWCNTs@r GO was better than other counter electrodes.The cyclic voltammetry and EIS electron transfer measurement showed that Zn S@N.f-MWCNTs@r GO films can provide fast electron transfers from the electrolyte to the CE and great electrocatalytic activity to reduce triiodide to a counter electrode based on Zn S@N.f-MWCNTs@r GO in the DSSC.