Preparation And Performance Optimization Of Carbon Based Counter Electrode In Dye-sensitized Solar Cell

The counter electrode of dye-sensitized solar cells?DSCs?is mainly responsible for the collection of electrons from the external circuit and catalytic regeneration of the redox couple of the electrolyte.The most common used counter electrode material is the noble metal Pt.Pt is rare and expensive.Therefore,the use of Pt electrode is one of the main reasons for the high cost of DSCs.Moreover,the catalytic activity of the counter electrode affects the power conversion efficiency of the DSCs to a certain extent.Therefore,the development of high-efficiency and low-cost counter electrodes is one of the most key scientific issues towards the development of of DSCs.In addition,As a strategic resource,Pt works as catalyst in the fields of national defense,chemical and energy industry.Based on our new enery strategy and there are resources strategy,the design low-cost and high-efficiency electrode materials to replace Pt is of important scientific research value.The merits of low-cost,good conductivity,high catalytic activity,rich sources,and other good characteristics of carbon material make it a rational catalyst to replace Pt.This dissertation focuses on designing novel carbon materials,performance optimization,and application in DSCs.Firstly,a novel carbon material with special morphology,denoted as carbon bead string?CBS?,was synthesized and used as counter electrode in DSCs.CBS is made of a series of carbon beads with a uniform diameter of 40⁵0 nm.The CBS showed a slightly lower catalytic activity towards the traditional I₃^-/I^-redox couple as compared with Pt and the power conversion efficiency of the corresponding DSCs using CBS counter electrode was up to 6.92%.It is noteworthy that the CBS counter electrode showed higher catalytic activity than Pt in the organic sulfide redox electrolyte?T₂/T^-?.The experimental results of nitrogen adsorption-desorption,electrochemical analysis,SEM,TEM,and other tests proved that this high catalytic activity of CBS could be attributed to a class of excellent electrode properties,such as large specific surface area,loose electrolyte diffusion channels,low reduction potential,and small charge transfer resistance anddiffusion resistance,etc.At the same time,carbon sphere?CS?with a uniform size was prepared.The CS showed high catalytic activity in the Co³⁺/Co²⁺redox electrolyte and power conversion efficiency of the DSCs was 8.50%.In order to further improve the catalytic activity of CS,a core-shell structure structured CS@Fe₃O₄ counter electrode material with para magnetic Fe₃O₄ nanoparticles as core and CS as the shell was developed.The CS@Fe₃O₄ can be directly adsorbed on magnetic substrate used as electrode.The experimental results proved that the catalytic activity of the CS@Fe₃O₄ magnetic electrode was significantly higher than both Fe₃O₄ and CS.When the DSCs used CS@Fe₃O₄ as the counter electrode,the power conversion efficiency was increased to 10.71%.Electrochemical analysis tests confirmed that the magnetic field of the electrode itself was conducive to the charge transfer process between the counter electrode and the electrolyte interface and the mass transport process of the electrolyte.In order to further prove that the magnetism of the electrode can enhance its catalytic activity,another kind of magnetic electrode material of Com@Fe₃O₄ was synthesized by loading Fe₃O₄ on mesoporous carbon?Com?.The experimental results presented that the Com@Fe₃O₄ also showed higher catalytic activity than both Fe₃O₄ and Com,the DSCs achieved a power conversion efficiency of 9.70%.In conclusion,the synthesized novel carbon materials of CBS and CS exhibit high catalytic activity which make them potential counter electrode materials in DSCs.At the same time,endowing the the counter electrode magnetic properties can improves the catalytic activity.The research opened up a new way to reduce the cost and improve the power conversion efficiency of the DSCs.