Preparation And Photoelectric Conversion Efficiency Of Cadmium-based Quantum Dots@N719 Dye Co-sensitized Solar Cells

Dye-sensitized solar cells（DSSCs）and quantum dots sensitized solar cells（QDSCs）are the third-generation solar cells that have been widely studied.In DSSCs,dyes such as N719,N3,etc.,act as photosensitizers that absorb a specific range of the solar spectrum.Inorganic semiconductor quantum dots（QDs）have the advantages of tunable band gap,high extinction coefficient,and multiexciton exciton generation（MEG）,and are often used as photosensitizers for QDSCs.Therefore,combining QDs with dyes to construct co-sensitized solar cells and broaden the solar spectral absorption range is one of the effective ways to improve the photovoltaic performance of solar cells.In this thesis,cadmium-based quantum dots and N719 dye are used to construct co-sensitized SnO₂ solar cells,which effectively enhance the photoelectric conversion efficiency of DSSCs.The study is as follows:1.Study of CdSe@N719 co-sensitized SnO₂ solar cells.Firstly,3-5 nm CdSe quantum dots were synthesized,and their absorption peaks were around 575 nm.On this basis,SnO₂ photoanodes coated with CdSe quantum dots were prepared,and the CdSe@N719 co-sensitized solar cells were assembled after dipping in N719 dye.The results of ultraviolet-visible absorption spectroscopy（UV-Vis）and electrochemical impedance spectroscopy（EIS）found that the introduction of CdSe quantum dots increased the light absorption range and light absorption intensity,increased the chemical capacitance,decreased the transfer resistance,and increased the number of photogenerated electrons in the cell.The photovoltaic performance test results showed that after 32 days of tracking tests,the short-circuit current density(J_sc)of the cell at stabilization（28 days）increased from 8.96 m A/cm² to 12.75 m A/cm²,the open-circuit voltage(V_oc)of 0.72 V remained unchanged,and the cell efficiency increased from 3.87%to 4.8%compared to N719-sensitized DSSCs.2.Study of CdSe/CdS@N719 co-sensitized SnO₂ solar cells.CdSe was used as the seed to cover the CdS shell layer with suitable thickness to obtain 6-8 nm CdSe/CdS core-shell quantum dots.On this basis,SnO₂ photoanodes coated with CdSe/CdS core-shell quantum dots were prepared,and the CdSe/CdS@N719 co-sensitized solar cells were assembled after soaking with N719 dye.The UV-Vis test results show that the absorption of CdSe/CdS is about 628 nm,which indicates that the addition of CdS shell layer can passivate the surface defects of CdSe quantum dots,increase the absorption of and enhance the photovoltaic performance of the cell.Testing the cell efficiency under standard conditions,the V_oc of the cell at stabilization（28 days）was0.73 V and the J_sc was 13.87 m A/cm²,giving a cell efficiency of 5.43%,an improvement of 45%compared to 3.73%for N719-sensitized DSSCs.3.Study of CdTe@N719 co-sensitized SnO₂ solar cells.Firstly,4-6 nm CdTe quantum dots were synthesized,and their absorption peaks were around 700 nm.On this basis,SnO₂photoanodes coated with CdTe quantum dots were prepared,and the CdTe@N719 co-sensitized solar cells were assembled after dipping in N719 dye.The EIS test revealed that the chemical capacitance of the cell increased and the transfer resistance decreased,which indicated that the coating of CdTe quantum dots by SnO₂could prevent the corrosion of CdTe by iodine electrolyte from affecting the photovoltaic performance of the cell.The photovoltaic performance test of the cell found that the introduction of CdTe quantum dots increased the short-circuit current density of the cells,and the J_sc of the cells increased from 8.96 m A/cm² to 13.27m A/cm² at stabilization（28 days）,resulting in an increase in cell efficiency from 3.87%to 5.11%.