Preparation And Properties Of Two Typical Luminescent Materials For Solar Cells

In recent years,solar photovoltaic power generation has received increasing attention as a typical representative of new energy technologies.However,for different types of solar cells,solving the problem of the mismatch between the solar spectrum and the solar cell’s absorption（spectral mismatch）has become the key to improving the performance of solar cells.For example,in silicon-based solar cells,due to the forbidden band width of silicon of 1.1 e V,light with energy above 1.1 e V（1100 nm）in sunlight forms heat losses in the form of lattice vibrations,while lower energy photons form transmission losses;Cs Pb I₃thin-film solar cells have good absorption of sunlight in the range of about 400-800 nm.Cs Pb I₃thin-film solar cells have a good photovoltaic effect on sunlight in the range of about 400-800 nm,however it is difficult to produce this effect on sunlight in the ultraviolet and far-infrared range.Therefore,by converting the light in the UV band,which is not susceptible to photovoltaic effect,into visible or infrared light,which is susceptible to photovoltaic effect,through spectral down-transfer materials,the problem of spectral mismatch can be effectively improved,thus increasing the solar light utilisation of solar cells.Based on the above ideas,the selection of suitable spectral down-transfer materials is the key.As a traditional rare earth doped solid light emitting material,phosphors are widely used in lighting and display applications due to their good absorption properties in the UV range,excellent light emitting properties and thermal stability.Due to the presence of the Eu²⁺4f-5d electron transition,Eu²⁺-doped phosphors usually have good luminescence properties,which is ideal for the study of spectrally downshifted materials.Therefore,in this paper,Eu²⁺-doped phosphors were used as the research object to design and prepare new light-emitting materials for solar cells through structural derivation and solid solution modification.The main results are as follows.（1）Green light is one of the best wavelengths for Cs Pb I₃solar cells to produce photoelectric effect.Green light phosphor K₂Hf Si O₅:Eu²⁺was prepared by high temperature solid phase method at 1120℃,and its crystal structure was analysed and studied by XRD structure refinement.The analysis shows that the K₂Hf Si O₅crystal is mainly composed of Si O₄tetrahedra and Hf O₆octahedra through shared O^2-forming the structural framework with four different K⁺lattice sites.The luminescence of K₂Hf Si O₅:Eu²⁺was investigated by spectroscopic tests and decay curves and the energy transfer between the different luminescence centres was found to be even-level-even-level.The use of K₂Hf Si O₅:Eu²⁺as the main raw material for the preparation of the energy-down-shift layer successfully improved the energy conversion of the Cs Pb I₃solar cell device,and the short-circuit current density of the encapsulated device increased by 1.41%and the photoelectric conversion efficiency increased by 2.75%compared to that of the bare cell.（2）K₂Ca PO₄F:Eu²⁺phosphor has a more suitable spectral matching band and high quantum efficiency with the photoelectric response curve of silicon-based solar cells in the red light band,but in the blue light band there is a part of the spectrum affects the photoconversion efficiency,so on the basis of the system has been used Cs partly instead of K,Mg partly instead of Ca successfully synthesized solid solution（K,Cs）₂（Ca,Mg）PO₄F:Eu²⁺phosphor,which successfully reduced the blue light band spectrum.On the basis of the 1.2-fold increase in the luminescence efficiency of the obtained solid-solution phosphor,this phosphor can be prepared into energy-down-shift layer with different thickness by epoxy A＆B.Under the optimum thickness,the photoelectric conversion rate of polycrystalline silicon solar cell is increased from 16.00%to 16.41%.