Quantum Dots Enhance The Performance Of Solar Cells And Mechanism Research

For a wide range of photovoltaic research,improving the photoelectric conversion efficiency（PCE）of solar cells is important.One of the main reasons for the low conversion efficiency of solar cells is the mismatch between the solar spectrum and the solar cells.Reasonable use of down-conversion mechanism and anti-reflection mechanismcan effectively improve the conversion efficiency of solar cells.The down-conversion mechanism converts ultraviolet photons,which are under-utilised by solar cells,into photons that can be absorbed by solar cells,while the down-conversion layer also creates an anti-reflection mechanism to increase solar cell conversion efficiency.In this contribution,investigates the luminescence properties of various quantum dots and analyses the luminescence mechanism of quantum dots through X-ray diffraction,transmission electron microscopy,fluorescence spectroscopy and solar cell characterization tests.To study the enhancement of solar cells by quantum dot layers,these quantum dot materials are applied to a variety of solar cells.In addition,simulations have been carried out to make the experimental results more reliable,as described below:CdSe quantum dots are used,which absorb photons of corresponding wavelengths when irradiated by light.CdSe quantum dots have high luminous intensity and large Stokes shifts.It has a high absorption intensity between 300-500 nm and a high photoluminescence（PL）peak at 628 nm by PL testing.It shows that the material has a very good down-conversion potential,and also shows the effect of anti-reflection in the reflectivity test.CdSe quantum dots have dual mechanism to improve the photovoltaic conversion efficiency（PCE）of solar cells,with a 9.83%relative increase in photovoltaic conversion efficiency from 14.45%to 15.87%for a hybrid structure with monocrystalline silicon solar cells.Simulations of the reflection reduction mechanism of the lower conversion layer were also carried out using the finite element method to simulate the presence of CdSe quantum dots on the surface microstructure of single crystal silicon solar cells.The results show that the presence of the quantum dots layer improves the absorption of sunlight,thereby increasing the conversion efficiency of monocrystalline silicon solar cells.CsPbX₃（X=Cl,Br,I）perovskite quantum dots have been synthesizedand apply it to silicon solar cells,after testing the solar cells can be derived from the results.Among the three types of quantum dots,CsPbBr₃quantum dots have the greatest improvement in solar cell PCE from 15.12%to 16.17%with a relative improvement of 6.94%,as the CsPbBr₃quantum dots synthesized by thermal injection method have a uniform size distribution and high colour purity.Based on the absorption and photoluminescence spectra it can be concluded that the quantum dots are suitable for down-shifting applications.The stability of CsPbBr₃quantum dots has been improved by coating the dots with Zn S and Al.The luminescence intensity of the dots has been increased.Simulations of Cs Pb Cl₃,CsPbBr₃and Cs Pb I₃quantum dot/crystalline silicon solar cells have also been carried out to investigate the effect on the solar cells by varying the thickness of the different layers.The results show that the presence of quantum dot layers has a certain effect on reducing the reflectance of crystalline silicon solar cells and improves the absorption of light by the solar cells.CsPbBr_xI_3-xquantum dots have been synthesized using a thermal injection method to find the x value that maximizes the efficiency improvement of Ga As solar cells by tuning the Br/I ratio.By absorption and photoluminescence tests it was demonstrated that emission at intermediate region wavelengths could be achieved.The emission peak of the CsPbBr_0.6I_2.4quantum dot is at 673 nm when x=0.6.CsPbBr₃and Cs Pb I₃quantum dots have a better luminescence wavelength compared to single halogen perovskite quantum dots.Therefore,they have a better down-shifting luminescence mechanism and better match the luminescence wavelength of solar cells.The most significant increase in efficiency was achieved by depositing CsPbBr_0.6I_2.4quantum dots on Ga As solar cells.The efficiency increased from 29.71%to 31.19%with a relative increase of 4.98%.This demonstrates that the presence of a quantum dot layer can increase the efficiency of Ga As solar cells and that the down-conversion mechanism is applicable to a wide range of solar cell surfaces.Finally,CsPbBr_xI_3-xquantum dot/Ga As solar cells are simulated to investigate the improvement of Ga As solar cells from the perspective of simulation.