Study On The Photovoltaic Performance Of Dye-sensitized Solar Cells Based On New Counter Electrode And Photoanode

Dye-sensitized solar cells?DSSCs?were first proposed by Michael Gr?tzel and Brian O'Regan in 1991.As a promising third-generation photovoltaic cell,DSSCs have attracted extensive attention of governments around the world and scientists due to the merits of easy fabrication,low cost,eco-friendliness,cost effective and flexible integration.A review of the development process in the past 20 years,each significant breakout in technology and performance was built on the optimization and innovation of material and structure.Through the unremitting efforts of scientists,the power conversion efficiency?PCE?of DSSCs has been increased from the original 7%to 13%,indicating the wide business application prospect.Generally,a typical DSSC device mainly consists of a photoanode,a sensitizer,a redox electrolyte and a counter electrode.Based on the previous studies,this paper mainly focus on the study of high-performance counter electrode and photoanode.The counter electrode plays a key role in collecting electrons from an external circuit,followed by catalyzing the reduction of tri-iodide?I₃^-?to iodide?I^-?.The mesoporous photoanode film is responsible for dye-loading and photoelectron transfer.On the one hand,this work explored new type of counter electrode.Further improvements in the electrocatalytic activity could be made by optimizing the material composition and microstructure of counter electrode.The structure optimization design of the mesoporous photoanode could improve the charge transfer process and suppressed unfavorable charge carrier recombination,resulting in an enhanced charge collection efficiency.The electrocatalytic ability and charge transfer dynamic process were systematically evaluated and analyzed by cyclic voltammetry?C-V?,electrochemical impedance spectra?EIS?,Tafel polarization,intensity Modulate photovoltage spectroscopy?IMVS?and intensity modulate photocurrent spectroscopy?IMPS?.Meanwhile,the corresponding theoretical results were verified by the photocurrent density-voltage?J-V?characteristics.This research mainly consists of the following four parts:1.Study on the electrocatalytic activity of new CNA counter electrode and photovoltaic performance?1?By using multi-walled carbon nanotube?MWCNTs?as raw material,ultra-flyweight carbon nanotube aerogel?CNA?with high porosity and surface area were prepared by means of sol-gel and freeze drying technologies.The surface morphologies and pore size distribution were characterized by field-emission scanning electron microscopy?FE-SEM?and nitrogen adsorption and desorption isotherms,respectively.?2?The electrocatalytic activity of CNA and Pt counter electrodes were evaluated and analyzed by cyclic voltammetry?C-V?,electrochemical impedance spectra?EIS?and Tafel polarization.?3?The overall performance of CNA and Pt counter electrodes were analyzed and compared in terms of cost and J-V characteristics.Research indicated that CNA counter electrode exhibited great advantage in raw material costs and manufacturing costs compared with Pt one.Moreover,DSSCs assembled with CNA counter electrode achieved the highest PCE of 8.04%,which was much higher than that of expensive Pt counter electrode-based DSSC?PCE=6.79%?.2.Study on the electrocatalytic activity of supporting CNA based counter electrode and photovoltaic performance?1?CNA decorated with Pt NPs?CNA-Pt?and CoS2 NPs?CNA-CoS2?were prepared by pyrolysis and hydrothermal method,respectively.The microstructure were investigated by X-ray diffraction?XRD?,FE-SEM,transmission electron microscopes?TEM?and nitrogen adsorption and desorption isotherms.?2?The electrocatalytic ability of CNA-Pt and CNA-CoS₂ counter electrodes were systematically evaluated and analyzed by CV,EIS and Tafel polarization.For reference,the corresponding electrocatalytic characterization of Pt and CNA counter electrodes were also carried out.?3?It was inevitable that the number of catalytically active sites increased with the increase in the Pt?Co S₂?filler content.However,the aggregation of Pt?CoS₂?also resulted in an obviously reduced pore size and pore volume,which was not favorable for the electrolyte diffusion.Hence,the content of Pt?CoS₂?should be well controlled to achieve the highest PCE.3.Effects of lattice distortion on the electrocatalytic activity of epitaxial strontium ruthenate?SrRuO₃?film counter electrode and its mechanism.?1?The epitaxial strontium ruthenate?SrRuO₃?films with the perovskite structure were sputtered on a?100?oriented MgAl₂O₄ single crystal substrate?denoted hereafter as SRO/MAO?and a?100?oriented SrTiO₃ single crystal substrate?denoted hereafter as SRO/STO?,respectively.The morphology of SRO/MAO and SRO/STO were characterized by FE-SEM and atomic force microscope?AFM?.?2?The crystal structures of SRO/MAO and SRO/STO film were systematically characterized by XRD.?3?The electrocatalytic ability of SRO/MAO and SRO/STO counter electrodes were systematically evaluated and analyzed by CV,EIS and Tafel polarization.?4?This work mainly focused on the effects of lattice distortion induced by the internal stress on the electrocatalytic ability and photovoltaic performance from a completely new perspective.This provides a fully new solution for the design of counter electrode with high catalytic activity.4.Study on the photo-generated charge transfer and photovoltaic performance for DSSCs based on Ti O₂/ITO/TiO₂?TIT?photoanode.?1?Owing to the high electron mobility and transparency in the visible range for ITO,TIT photoanode structure was proposed in this work.The microstructure of photoanode were investigated by FE-SEM,XRD and energy dispersive spectrometer?EDS?.?2?The charge transfer and recombination of TIT and conventional TiO₂ photoanodes were systematically characterized and analyzed by IMVS,IMPS and EIS.?3?Owing to the poor dye adsorption capacity on ITO nanoparticles,the thickness of ITO interlayer needed to be optimized to balance the charge transfer and recombination,thereby achieving the optimal photovoltaic performance.