Controllable Synthesis Of CdS And Application Of S^2- In CdS Quantum Dot Solar Cells

As one of the most promising third-generation photovoltaic devices,quantum dot sensitized solar cells have attracted more and more attention because of their simple fabrication,low cost,and potential high efficiency.Therefore,we continue to improve their photoelectric conversion efficiency and device stability by accurately optimizing the material structure and device structure.In the process of the development of the quantum dot solar cells,it is worth mentioning that metal chalcogenide semiconductor as a sensitizer to capture sunlight,as the electrode catalytic electrolysis.However,at present,the performance of quantum dot solar cells is far from the theoretical value,even lower than the traditional solar cells.The main reasons for the low performance of quantum dot solar cells are as follows:the crystallinity of quantum dots obtained by the traditional quantum dot synthesis method is poor,the size is uneven and difficult to control,and the loading rate of quantum dots is low,while the long-chain configuration of organic synthetic quantum dots will form an insulating layer hinder the transmission of carriers and affect the performance of quantum dots.To solve these problems,this paper uses two methods:high-temperature hot injection to control the synthesis of quantum dots,S2-ligands to modify the interface of quantum dots,and S2-as an auxiliary linker to improve the loading of quantum dots.It is to obtain more efficient quantum dot sensitized solar cells.This paper consists of four chapters.The first chapter is the introduction part.It systematically introduces the development process,working principle,main sensitizer classification,interface modification means and development trend of quantum dot sensitized solar cells.It discusses the advantages and disadvantages of different sensitizers and improvement methods,as well as several commonly used interface modification means,and proposes S2-as the modified material Chapter 2 and Chapter 3 are the experimental part,which respectively introduces the controllable synthesis of CdS quantum dots and the influence of using S2-to modify the interface on the performance of QDs,and the influence of using S2-as the auxiliary linker on the performance of QDs sensitized solar cells.The main contents are as follows:(1)CdS quantum dots with uniform size and good crystallinity were synthesized by high-temperature thermal injection method,using CdO as a cadmium source,elemental S as a sulfur source,oleic acid,and Octadecenylamine as ligands.By controlling the reaction time,the quantum dots were synthesized controllably.NMF solution to Na2S was used as S2-ligand Volution to modify the surface of CdS quantum dots coated into an organic long chain.The changes of CdS quantum dots after surface modification were analyzed by TEM,XRD,and UV-Vis absorption spectra,and the properties of modified CdS quantum dots were studied by photoluminescence spectra and transient fluorescence spectra.It is proved that the surface modification of CdS quantum dots with S2-does not affect its lattice structure,and the fluorescence peak of CdS quantum dots is sharpened after surface modification with S2-,the half-peak width was reduced from 75 nm to 50 nm,and the characteristic peaks of quantum dot defects were effectively reduced.The fluorescence lifetime was increased from 15.39 ns to 124.315 ns.This shows that the interface modification of CdS quantum dots using S2ligands is beneficial to improve the performance of CdS quantum dots.(2)To improve the loading of quantum dots,it is proposed to use S2-ligand solution obtained from Na2S dissolved in NMF as an auxiliary linker,and to use in-situ auxiliary linker method to oxidize CdS quantum dots through S2-linkage to TiO2 metal photo-anode method,the number of deposition layers of auxiliary connecting agent and the thickness of photo-anode is used as variables.Through electrochemical J-V,EIS,OCVD,IPCE,and energy spectroscopy system,the deposition cycle of different photo-anode thickness and different auxiliary agents are systematically studied.The electrochemical performance of the QDSCs was counted,and it was concluded that the device under the auxiliary SILAR 3 times ZnS passivation layer had the best photovoltaic performance when the thickness of the metal oxide photoanode was 21μm and the number of auxiliary connector deposition cycles were 10,Its photoelectric conversion efficiency reached 2.38%.