Fabrication Process And Structure Design Of Spectral Down-conversion Solar Cells

Solar energy is a kind of abundant,safe and clean energy.Therefore,converting solar energy into electricity has become a hot research area in the past decades.Currently,crystalline silicon solar cells is the main technology in this field.However,the low utilization rate of short-wavelength photons in the solar spectrum leads to high energy loss,which seriously hinders the performance improvement and application development of crystalline silicon solar cells.The introduction of spectral down-conversion materials onto the crystalline silicon solar cells converts incident short-wavelength photons into long-wavelength photons,which can reduce the photon loss in the short-wavelength band and is an effective way to improve the conversion efficiency of the solar cells.The main contents of the paper are as followings:（1）Analyse the feasibility of CaAlSiN₃:Eu²⁺as a spectrum down-conversion material from the perspectives of crystal structure and luminescence mechanism.The testing results show that the peak wavelength of the CaAlSiN₃:Eu²⁺excitation spectrum is 430nm,and that of the emission spectrum is 610nm,which can realize down-conversion of the spectrum and has the potential to improve the photoelectric conversion efficiency of monocrystalline silicon solar cells.（2）The effects of two preparation processes（down-conversion thin films and screen printing）on the performance of monocrystalline silicon solar cells was compared and studied.The results show that both photoelectric conversion efficiency of the two samples made by two different preparation processes is improved after packaging.Among them,the photoelectric conversion efficiency of the sample made by down-conversion thin film method is relatively increased by 1.589%,and the relative increase of the sample using the screen printing method is 1.060%,indicating that the down-conversion thin film method can bring better performance improvements to monocrystalline silicon solar cells.（3）The effect of CaAlSiN₃:Eu²⁺red phosphor particle size on the performance of monocrystalline silicon solar cells was explored.First,the CaAlSiN₃:Eu²⁺red phosphor was classified according to the particle size,and the samples with different particle sizes were obtained.The test results show that when the CaAlSiN₃:Eu²⁺red phosphor particle size is in the range of 5-20μm,the larger the particle size,the greater the CaAlSiN₃:Eu²⁺excitation light intensity and emission light intensity,and the better the luminous performance.Then use the sorted phosphor samples to prepare down-conversion thin films and apply them onto the cells.Comparison between the test results before and after the cell’s encapsulation shows that the four samples using phosphors of different particle sizes have the same change trends in surface reflectance and external quantum efficiency.The sample using 8-10μm particles has the highest relative increase,with an increase of 4.477%,the sample using 10-15μm has a relative increase of 3.248%,and the other two samples have small increases after packaging.It shows that CaAlSiN₃:Eu²⁺red phosphors with the particle size of8-15μm can bring greater performance improvement to monocrystalline silicon solar cells.The reason is that the 8-15μm size CaAlSiN₃:Eu²⁺particles have the smaller number of crystal defects,and the moderate size allows the excitation light to reach the luminous center.