The Performance Research Of CdS Quantum Dot Sensitized Solar Cells Based On MWCNTs Counter Electrodes

The quantum dot sensitized solar cells(QDSCs)gain the wide attention because of simple production process,cheap raw materials and high theoretical efficiency.QDSCs utilizing inorganic semiconductor quantum dots(QDs)as light harvesters are extremely appealing due to the outstanding optical and electrical properties of QDs,such as high absorption coefficient,tunable size-dependent bandgap and possibilities of multiple exciton generation.CdS with a proper bandgap of 2.25 eV as one of the most common quantum dot sensitizers has been widely reported.However,the power conversion efficiency(PCE)and stability of CdS QDSC are poor.Since the conduction band of ZnS is higher than that of CdS,it can prevent electrons recombination and then improve the efficiency of electron collection in CdS QDSCs.It seems to be an optimal way when mixed-joint CdS/ZnS are used to cosensitize quantum dot sensitized solar cells.It is different of traditional deposition.It is can be found that the PCE of QDSC with mixed-joint CdS/ZnS(6.370 %)is higher than that of traditional CdS/ZnS(4.12 %).Precious metal Pt is a common counter electrode(CE)material.However,the development of Pt as CE material has been limited due to its high price and reactions with electrolytes.The multi-wall carbon nanotubes(MWCNTs)are considered the excellent material as CE due to rapid electron transfer nature and extraordinary specific surface area.However,when the MWCNTs as the second-class catalytic activity material are applied to CE of QDSCs,the cell possesses an unsatisfactory PCE.Therefore,nanograghite with high electrical conductivity or CuS with outstanding catalytic activity is introduced to improve the performance of CE.By adding nanograghite,the catalytic activity of MWCNTs CE is obviously improved.The PCE of QDSC increased by 0.158 % after adding nanograghite.There are threemethods to introduce CuS,such as successive ionic layer adsorption and reaction(SILAR)method,spin coating method and one step synthesis method.By three methods,the catalytic activity and PCE of CE are increased due to increasing active sites.Among them,the performance of CE with one step synthesis method is optimal.The charge transfer resistance of Pt CE is two times as big as that of one step synthesis method.The PCE is 1.240% higher than that of the Pt CE.