Preparation Of CdX(X=S,Se,Te) Quantum Dots And Study Of The Performance Of Sensitized Solar Cells

Since the late 1970’s,quantum dots(QDs)have attracted broad attention of the scientists.Compared with the traditional organic dyes,QDs performs excellently in many novel properties.The quantum size effect and multi-exciton effect of QDs were well applied in the quantum dot sensitized solar cells(QDSSCs).Nowadays,QDSSCs is still in the stage of primary development,and how to improve the rather low photoelectric conversion efficiency has become the common goal of the researchers.As the core part of QDSSCs,QDs have directly effects on the photoelectric conversion efficiency of solar cells.In this paper,Cd Te QDs modified by POSS were prepared in aqueous phase.The photoelectric properties of the POSS-Cd Te QDSSCs were studied.Cd Se Te alloy QDs was also prepared in aqueous solution.A preliminary research was carried out on the performance of Cd Se Te QDSSCs.The main research contents are as follows:(1)Study on preparation conditions of Cd Te QDs: Cd Te QDs were synthesized in aqueous phase using NAC as the stabilizer by heating for different time.The effects of different growth conditions(NAC/Cd ratios,Cd/Te ratios,p H values)on the growth and optical properties of QDs were studied.The results showed that when NAC/Cd/Te=1.2:1:0.2 and p H=11.5,the QDs had the fastest growth rate and the fluorescence quantum yield reached 80%.(2)Preparation and condition optimization of Cd Te-Cd S QDSSCs: The prepared Cd Te QDs were successfully connected on the surface of Ti O2 films by the aid of bifunctional molecular linker(TGA).A layer of Cd S was introduced as the transition layer between Cd Te and Zn S using SILAR method.The QDs sensitized working electrode and polysulfide electrolyte and Cu S counter electrode were assembled into Cd Te-Cd S QDSSCs.The effects of TGA addition amount,p H value of QDs solution,sensitization time,Cd S post-treatment times and Zn S post-treatment times on the solar cell efficiency were studied.The optimum process parameters were determined: TGA was added to 10μL,p H=10.38,the sensitization time was 24 hours,the number of cycles of Cd S and Zn S was 4 and 2,respectively.(3)Study on performance of POSS-Cd Te QDSSCs: First,Cd Te QDs were prepared in the aqueous phase,and then OA-POSS was coupled to the surface of Cd Te QDs by coupling agent EDC.The QDs before and after modification were applied to QDSSCs to study the change of cells performance.The results showed that the current density of the cells increased from 4.056 m A/cm2 to 5.806 m A/cm2,energy conversion efficiency increased from 2.04% to 2.97%,which increased by 46%.The IPCE curve of the cells showed that the maximum conversion efficiency of the incident monochromatic photon-to-electron was increased from 40% to 53%.The EIS analysis showed that the charge transfer resistance R2 values of the Cd Te and POSS-Cd Te cells were 142 ? and 166.2 ?,respectively.And the electron lifetime increased from 894 ms to 1083 ms.The surface modification of QDs by OA-POSS can inhibit charge recombination between the interface of Ti O2 and electrolyte and improve the electron injection and collection efficiencies of the solar cells.(4)Preparation of Cd Se Te QDs and study on the performance of QDSSCs: Cd Se Te QDs were synthesized in aqueous phase,and the effects of different experimental parameters(Se/Cd ratios,Cd/Te ratios,p H values)on the growth and optical properties of QDs were discussed.The Cd Se Te QDs were assembled into QDSSCs to study its photoelectric properties.The results showed that when the heating time is 7.5 h,the current density reached 5.53 m A/cm2,and the energy conversion efficiency is 2.9%.