A Comparative Study Of The Effects Of Spectral Down Conversion Materials Containing Cerium And Europium On Monocrystalline Silicon Solar Cells

Along with the reformation of energy structure deepening,solar energy attracts more and more attention because of its prominent merits,including cleanliness,safety and sustainability.At present,people mainly use solar energy by convert light into electrical energy through solar cells.Silicon solar cells are one kind of widely used solar cells.However,this kind of solar cells have the problem of low utilization of short wavelength photons.This problem limits its further development.The causes of this problem can be summarized as the following two aspects:First,higher surface reflectance of short wavelength photons results in these photons cannot excite the electron-hole pairs;second,the energy of short wavelength photons is higher than the band gap of silicon solar cells.This mechanism results in some energy loss.One way to improve the utilization efficiency of short wavelength photons is to convert it into long wavelength photons by spectral down conversion effect,and the phosphors are the main sources of materials that with this effect.YAG:Ce³⁺is a kind of phosphors which widely used in white LED field,and it have been proved to improve the performance of monocrystalline silicon solar cells.However,the emission intensity of YAG:Ce³⁺is lower,as is the excitation efficiency in the range of 370-400nm.These factors affect the application prospect of this phosphor as spectral down conversion materials.Based on the study of rare earth luminescent materials,Eu²⁺-activated CaAlSiN₃ phosphors(CaAlSiN₃:Eu²⁺)were selected as new spectral down conversion materials.Comparative study of the effects of two kinds of phosphors on solar cells by printing phosphors on monocrystalline silicon solar cell.The main contents of the study are as follows:（1）The fluorescence characteristics of YAG:Ce³⁺and CaAlSiN₃:Eu²⁺were measured by depositing these two kinds of phosphors on quartz glass substrate.It can be found that,comparing with YAG:Ce³⁺,CaAlSiN₃:Eu²⁺phosphors have wider excitable band range and higher emission intensity.Then,the size and shape of two kinds of phosphors were observed by SEM.SEM photos show that the shape of YAG:Ce³⁺phosphors is approximately spherical,while the shape of CaAlSiN₃:Eu²⁺phosphors is approximately rectangular.（2）The effects of CaAlSiN₃:Eu²⁺and YAG:Ce³⁺on the monocrystalline silicon solar cells were compared.First,two kinds of phosphor--organic mixed slurries were made by adding phosphors into organic materials.Then,these two kinds of slurries were printed on monocrystalline silicon solar cells respectively by manual screen printing.Finally,two kinds of samples were prepared by packaging the solar cells and quartz glasses together by EVA.The effects of two phosphors on monocrystalline silicon solar cells were analyzed and compared from four perspectives respectively,including surface reflectance,external quantum efficiency,Ⅰ-Ⅴ characteristics and photoelectric conversion efficiency.The experimental results show that,in short wavelength range,the surface reflectance of two samples have decreased after packaging.The external quantum efficiency and photoelectric conversion efficiency have improved,and the increase of these parameters of sample with CaAlSiN₃:Eu²⁺are larger than that of YAG:Ce³⁺.The photoelectric conversion efficiency of the sample with CaAlSiN₃:Eu²⁺has increased by 0.203%,from 19.159%to 19.362%,while the photoelectric conversion efficiency of the sample with YAG:Ce³⁺has increased by0.094%,from 19.155%to 19.249%.There are two fundamental reasons for the different increase of photoelectric conversion efficiency.First,the fluorescence characteristics of CaAlSiN₃:Eu²⁺are much prominent than that of YAG:Ce³⁺,and it help the solar cells improve the utilization efficiency of short wavelength photons.Second,the simulation of light transmittance of phosphor particles was designed.The simulation results show that,in the visible band range,the light transmittance of CaAlSiN₃:Eu²⁺is higher than that of YAG:Ce³⁺.It indicates that monocrystalline silicon solar cells will receive more photons when CaAlSiN₃:Eu²⁺is used as spectral down conversion materials.