Preparation Of CuInSe₂ And Zn Doped CuInSe₂ Quantum Dots By Thermal Injection And Characterization Of Sensitized Cells

CuInSe₂quantum dot materials,as the representative of three quantum dots,have attracted wide attention in recent years due to their advantages of adjustable light absorption range,good light stability and high internal dipole moment which is convenient for charge separation.CuInSe₂quantum dot materials are direct band-gap semiconductors with absorbance coefficient up to 10⁵cm^-1and band-gap matching with solar spectrum.As a photosensitizer applied in the third generation of solar cells.CuInSe₂quantum dots were synthesized by thermal injection method in this paper and CuInSe₂quantum dots doped with zinc were modified.By means of XRD,U-V,PL spectrum,TEM and XPS,the controlling factors of quantum dot size distribution and the influence of experimental conditions on optical properties were studied.The photoelectric properties of solar cells were studied by synthesizing high quality CuInSe₂quantum dots and Zn-CuInSe₂quantum dots as sensitizers.Specific research contents are as follows:(1)The high quality CuInSe₂quantum dots were synthesized by high temperature injection in a three-nosed flask with selenium powder completely dissolved in oleoamine(OAM)and diphenyl phosphorus(DPP)as selenium source precursors,and oleoamine and octadecene as solvents of cuprous iodide and indium acetate.By changing the experimental time(5 min,10 min,20 min)and the experimental temperature(160?,180?,200?,220?)to control the size of the quantum dots,the controlling factors of the size distribution were studied,and the regulation mechanism of optical properties was explored.The results showed that the size of the quantum dots was controlled through the temperature of heat injection and the holding time.The quantum dots generated grew in size in the range of 4.7 nm-8.5 nm,with a band gap range of 2.35 e V to 1.7 e V,and the edge of the light absorption band was red shifted.Through comparison,it is found that the best optical properties of chalcopyrite CuInSe₂quantum dots can be generated at about 6.5nm by heat injection temperature of180? and holding for 5 min.(2)The holding time of 5min was selected to further improve the process conditions for the synthesis of quantum dots.When the heating strategy is 160?,180?,200?,220?,the selenium source precursor is injected,and the CuInSe₂quantum dots are modified by doping Zn element.XRD,PL,U-V,TEM and other methods were used to find that the size of Zn-CuInSe₂quantum dots generated at different temperatures was relatively uniform at about 4.7 nm,the absorption band edge was up to 835 nm,and the emission spectrum of PL was 694 nm.Compared with CuInSe₂quantum dots,the size of Zn-CuInSe₂quantum dots decreased,the uniformity improved,and the absorption range increased.In addition,the intensity enhancement peak of PL emission spectrum due to the size effect of quantum dots is blue shifted,and the optical properties are improved,which proves that the doping of Zn element modifies the defects of CuInSe₂quantum dots.(3)The oily quantum dots of the OAM ligand were converted to water-based quantum dots by trimercaptopropionic acid,and then the quantum dots were deposited on titanium oxide.The double group of the ligand was used as the efficient medium between titanium dioxide and quantum dots and between quantum dots and polysulfide electrolyte.EDX proved that the elemental composition of the quantum dots remained unchanged after adsorption to the photoanode.CuInSe₂quantum dots and Zn-CuInSe₂quantum dots were respectively used to assemble the photoanode cells,and finally the quantum dots sensitized solar cells with PCE of 1.05%and 2.66%were fabricated.