The Research Of New Thin-film Solar Cells Based On Sulfide And Its Composite Counter Electrode

With the increase of human demand for energy and the intensification of environmental pollution,environmentally-friendly renewable energy sources have become more and more important.As the third generation of solar cells,dye-sensitized solar cells?DSSCs?have the advantages of low preparation cost,simple manufacturing process,high theoretical conversion efficiency,can be made into flexible and color-adjustable devices,and can be combined with buildings.So it has received extensive attention and research.DSSCs usually consist of a dye-sensitized nanocrystalline TiO₂ film,an electrolyte containing a redox couple and a counter electrode?CE?.The counter electrode is responsible for receiving electrons from an external circuit and transmitting them to the redox couple,which promotes the reduction of redox couple.The traditional counter electrode material is usually made of platinum?Pt?,but Pt is expensive and scarce,and it is easily corroded by the electrolyte,which affects the large-scale promotion and stability of DSSCs.Therefore,it is necessary to develop a counter electrode material with excellent performance and low cost to replace the Pt.Sulfides are direct band gap semiconductors with excellent optoelectronic properties and have been widely used in the field of catalysis.However,the poor conductivity of sulfide limits its application effect.In this work,sulfides with good catalytic properties were combined with carbon nanofibers?CNFs?and nickel?Ni?foam with excellent electrical conductivity,respectively.And they were applied to the counter electrodes of DSSCs to further explore the photovoltaic performance of DSSCs.The specific research content is as follows:?1?Bi₂S₃/CNFs composites were synthesized by simple electrospinning technology and hydrothermal method.And by adjusting the amount of Bi₂S₃,Bi₂S₃ nanoparticles were densely grown on CNFs without agglomeration.The Bi₂S₃/CNFs composites were applied to the counter electrode of DSSCs.Based on the high catalytic activity provided by Bi₂S₃nanoparticles and the fast electron transmission channel provided by the network structure formed by one-dimensional CNFs,the optimized Bi₂S₃/CNFs composites counter electrode shows excellent electrochemical performance.A photoelectric conversion efficiency?PCE?of7.64%higher than Pt counter electrode?7.12%?was achieved.Based on low cost and simple manufacturing process,Bi₂S₃/CNFs composites counter electrode has a very good prospect.?2?1T-2H hybrid MoS₂ nanosheets and NiS/Ni₃S₂?NS?nanoparticles were grown on the surface of CNFs by glucose-assisted hydrothermal method?NMS/CNFs?.After the CNFs were completely coated with MoS₂ nanosheets,a large amount of NS nanoparticles were loaded on the outer layer without agglomeration.Because of the high catalytic activity of sulfides,the high electrical conductivity of carbon,and the excellent one-dimensional structure of nanofibers,NMS/CNFs composites exhibit excellent electrochemical performance.The photoelectric conversion efficiency of DSSCs with NMS/CNFs composites counter electrode reached 8.40%,which is higher than Pt counter electrode?7.52%?,indicating the great potential of NMS/CNFs composites counter electrode.?3?NiCo₂S₄ nanotube arrays were grown in situ on Ni foam by a two-step hydrothermal method,and the growth morphology of the nanotube array was optimized by adjusting the amount of chemicals.NiCo₂S₄ nanotubes are densely and orderly grown on a three-dimensional structure of Ni foam,and the growth direction is approximately perpendicular to the surface of the Ni foam.The nanotube wall is thin and has a porous structure.With its excellent chemical composition and nanostructure,and the selection of a suitable conductive substrate,NiCo₂S₄nanotubes/Ni foam shows very excellent catalytic performance.The NiCo₂S₄ nanotubes/Ni foam were used as counter electrode for DSSCs,and its photoelectric conversion efficiency reached 8.29%,which is much higher than Pt counter electrodes?7.48%?.Therefore,the NiCo₂S₄ nanotube/Ni foam counter electrode has very good reference significance for the future development of electrode materials.