Design And Application Of Graphene-based Materials In Counter Electrode Of Dye-sensitized Solar Cells

Exploring clean energy is the only way for human sustainable development.Dye-Sensitized Solar Cells,as the third-generation solar cells,exist only in the experimental stage.The main reason is that the preferred material for the counter electrode is the noble metal-platinum?Pt?.Therefore,the current research direction is mainly Pt replacement material.The counter electrode should have the following advantages:high catalytic activity,high electrical conductivity,high reflectivity,low cost,high surface area,porosity,optimum thickness,chemical and electrochemical and mechanical stability,chemical corrosion resistance,good adhesion to TCO conductive glass,etc.Based on the above analysis,the research of this subject is mainly based on the design of graphene materials,and its research and preparation can achieve the same photo-electric conversion performance?PCE?as Pt electrodes.On the one hand,graphene was reduced by three reduction methods,and it was found that reducing glutathione is more thorough than ascorbic acid?VC?and 800°C high temperature reduction,which is beneficial to material properties;on the other hand,the layer-layer is assembled by the difference in zeta potential between molybdenum disulfide and graphene at a low pH.Then,by adding single-walled carbon nanotubes to increase the conductivity of the system and inhibiting the agglomeration of the graphene sheets to increase the specific surface area of the material,the performance of the composite electrode is enhanced.The main research results are as follows:?1?According to different reduction methods,the degree of reduction of GO from large to small is followed by reduction of glutathione,VC,800°C high temperature,G-?material contains the least amount of oxygen,resulting in increased conductivity of G-?counter electrode In addition,because G-?has the highest degree of macropore defects,the electrocatalytic performance of the material itself is increased.Since the reduction of GO by glutathione is more complete than the reduction of VC,the surface oxygen-containing functional groups of the graphene in the G-?having the smallest SSA are reduced.Among the three reduction methods,the G-?material exhibited the highest PCE?5.89%?,which was mainly attributed to the high degree of reduction,which improved the conductivity and the high electrocatalytic performance caused by the high degree of defects.?2?A composite electrode was prepared by different zeta potentials of molybdenum disulfide?MoS₂?and graphene at different pH.After mixing a single layer of MoS₂ solution with GO,the pH value is 3.0.In this environment,the zeta potential of the surface of MoS₂ is a positive potential,and the surface of the GO is a negative potential.It can be seen by TEM analysis that the two are layer-layer bonds.Finally,the composite electrode obtained a PCE of 6.01%,which was slightly smaller than that of the Pt counter electrode.?3?Single-walled carbon nanotubes were added in the composite material based on layer-layer assembly of a single layer of MoS₂ and graphene.On the one hand,the conductivity of the material itself is increased,which facilitates the rapid transport of electrons.On the other hand,the expansion of the carbon nanotubes in the middle of the graphene sheet layer weakens the agglomeration of the graphene layer and increases the SSA of the material,thereby increasing the contact sites between the electrodes and the electrolyte.The DSSC assembled by the composite electrode GTM5 thus obtained can achieve a PCE of 7.43%,which is higher than the Pt electrode,and is a Pt-free material.