Study On Surface Color Difference And Optical Absorption Properties Of Polycrystalline Silicon Photovoltaic Cells And Modules

Study on surface color difference and optical absorption properties of polycrystalline silicon photovoltaic cells and modules is one of the current frontier research topic in the field of renewable energy on the photovoltaic cell surface optical structure research direction.The results are helpful to improve the absorption and utilization of solar energy and have broad prospects and profound application value in photovoltaic industry.Therefore,people attach great importance to it.In this thesis,by means of theoretical analysis,simulation calculation and experimental detection,the color difference and optical absorption properties of photovoltaic cell surface optical structure are systematically and deeply studied.According to the superposition of absorbed energy of each wavelength,the optical absorption properties of photovoltaic cell surface under different solar spectral irradiance distribution were simulated by using transfer matrix method to obtain the optimal surface optical structure.According to the principle of statistical dispersion degree,the color values of samples in strict system were determined by the reflectivity judgment method at sensitive wavelength,and the dual-beam coaxial laser color detection system was designed.The color decision values of the samples were detected and the color intervals of the samples were demarcated with the help of human eye recognition to achieve color classification of polycrystalline silicon photovoltaic cells.The multi-beam coaxial laser spot scanning detection system is preliminarily designed to detect the optical absorption properties of photovoltaic cells comprehensively.The surface optical structure of black silicon of photovoltaic cells and modules was optimized through three comparative experiments to improve the performance.These works have obtained innovative research results,which have promoted the academic and industrial development to a certain extent.The main research contents and achievements of this thesis are as follows:Complete process parameter system description of polycrystalline photovoltaic cells and modules:The complete process system related to the surface optical structure of photovoltaic cells and modules is studied.Firstly,the principle and industrial chain of crystalline silicon photovoltaic cells are analyzed,and the main differences between polycrystalline silicon cells and monocrystalline silicon cells are analyzed.Secondly,the surface color and optical absorption of polycrystalline photovoltaic cells in the texturing process and coating process are analyzed primarily.Then the effects of structure and packaging are studied in the module process.Finally,the main photoelectric performance parameters of polycrystalline silicon photovoltaic cells and modules are analyzed.Through the analysis of the whole process,a complete process parameter system about the surface color difference and optical absorption was established.Study on the correlation between the surface color difference and the thickness of antireflective film of polycrystalline silicon photovoltaic cells and design of the optimal thickness of antireflective film:In the simulation of transmission matrix method,the optimal thicknesses of antireflection film of polycrystalline silicon photovoltaic cells under different solar spectral irradiance distribution were obtained by superposition of absorbable power density of each wavelength.An idea of simulating the surface optical structure parameters based on the distribution of specific solar spectral irradiance is proposed.The influences of different surface optical structures on color difference and optical absorption properties of polycrystalline silicon photovoltaic cells under different solar spectral irradiance distribution were analyzed by analog simulation.Starting from the problem of color difference on the surface of polycrystalline silicon photovoltaic cell,the antireflective film thickness,refractive index and reflective spectrum of polycrystalline silicon photovoltaic cells with different colors were tested experimentally.It was found that the surface color difference with stable refractive index was mainly caused by the different thickness of antireflective film.According to the actual sample parameters,the optical absorption of the surface structure of polycrystalline silicon photovoltaic cell is simulated by using the transfer matrix method,and the simulation results are in good agreement with the experiment.According to the spectral irradiance distribution of incident light,the maximum total power density of absorbable light was simulated by multiplying the power density of each wavelength and the corresponding absorption rate and then superposing the products.The optimal antireflective film thickness can be obtained.Thus,the optimal surface optical structure of polycrystalline silicon photovoltaic cells is designed.Based on the standard solar spectral irradiance distribution,the results show that the light with the maximum power density can be absorbed when the refractive index is 2.05 and the thickness is 62 nm.By comparing the optimal antireflective film thickness under different spectral irradiance distribution,it is found that the optimal antireflective film thickness of polycrystalline silicon photovoltaic cell will be different due to the different spectral irradiance distribution.According to the solar spectral irradiance distribution in different regions,the idea that photovoltaic cells can be customized to obtain the best light absorption is proposed.Construction of strict surface color determination and discrimination method for polycrystalline silicon photovoltaic cells:A method of reflectivity judgment at sensitive wavelength was proposed to determine the color value of samples,and a dual-beam coaxial laser color detection system was established to realize color classification.A multi-beam coaxial laser spot scanning system is proposed to detect the light absorption properties of samples at different positions,wavelengths and light intensities.The strict color values and color model of polycrystalline silicon photovoltaic cells were established by the reflectivity judgment method at sensitive wavelength.Based on this,a dual-beam coaxial laser color detection system was designed.With the help of human eye recognition,the color discrimination is realized more accurately.A similar scheme for detecting optical absorption is designed preliminarily.Based on the color classification of information of human eye recognition,a color model related to spectroscopy is designed,and the relationship between color information and spectral information is established.By calculating the standard deviation of reflectivity which describes the degree of dispersion in statistics,the reflectivity judgment method at sensitive wavelength is established to determine the strict color value,the sensitive band and insensitive band of samples for color detection.A dual-beam coaxial laser color detection system was designed.The system can be used to test and classify the color of samples.The method is applied to the color sorting problem of polycrystalline silicon photovoltaic cells.According to the statistical calculation of reflection spectrum of a large number of polycrystalline silicon photovoltaic cells,the color value database of polycrystalline silicon photovoltaic cells is established according to the reflectivity judgment method at sensitive wavelength.The sensitive wavelength value is434 nm and the insensitive wavelength value is 645 nm,forming the selection range of the laser wavelength of the detection system.A dual-beam coaxial laser color detection system for polycrystalline silicon photovoltaic cells color detection was built by selecting two laser sources with narrow band wavelength.The system is used to test the polycrystalline silicon photovoltaic cells which have been classified by human eyes.Then a strict database of color decision values of polycrystalline silicon photovoltaic cells is established and the color intervals are demarcated.The experimental results show that the color classification can be accomplished by using this system for the new polycrystalline silicon photovoltaic cell.This technology can replace the traditional sorting by human eye and provide conditions for automatic color sorting.A set of multi-beam coaxial laser spot scanning detection system was designed preliminarily to detect the optical absorption of photovoltaic cells.Spot scanning can be carried out on the sample to analyze the light absorption of various parts of the surface by laser focusing method.The light absorption of photovoltaic cells in different wavebands can be analyzed by multi-wavelength beam.And the light absorption of photovoltaic cells in different light intensity conditions can be analyzed by laser energy regulation.It can detect the surface light absorption properties of samples at different positions,different wavelengths and different light intensity.The system can detect the light absorption of photovoltaic cells according to the distribution of solar spectral irradiance in the area where photovoltaic cells are used,which provided the design solutions for the customized testing of photovoltaic cells in specific areas.Establishment of technical scheme for improving the photoelectric performance of polycrystalline silicon photovoltaic cells and modules:based on the black silicon surface,the production process was improved through comparative experiments to improve the photoelectric performance of photovoltaic cells and modules.And the optimal multilayer structure was designed through simulation.Firstly,the difference of silicon surface structure caused by diamond wire cutting instead of traditional silicon carbide particle suspension cutting is discussed.Then,the selection of lotion in the pre-cleaning process matching the black silicon surface was analyzed.Using HF/HNO₃ lotion can make the black silicon wafer have higher light trapping performance,thus improving the photoelectric conversion efficiency by nearly 0.154%.The specific operation process and the role of the new thermal oxidation process in the production of polycrystalline silicon black silicon photovoltaic cells were studied.Taking oxygen flux as the control point,the photoelectric conversion efficiency is improved by 0.11%when the optimal oxygen flux is2200 cubic centimeters per minute compared with that without thermal oxidation process.Based on polycrystalline silicon photovoltaic module structure,in view of the common components on the market,through the combination of multiple components selection,The effects of different components for polycrystalline silicon photovoltaic modules are analyzed.The experimental results show that the dual-glass black silicon photovoltaic module using twill soldering strip has the best photoelectric performance.Compared with the traditional single glass black silicon photovoltaic module,its output power is increased by 6.13W.Finally,the method based on transfer matrix method combined with solar spectral irradiance distribution to calculate the optimal thickness was applied to the silicon dioxide film formed by thermal oxidation process.The optimal thickness of multilayer antireflective film for a new photovoltaic cell surface structure under standard solar spectral irradiance distribution is obtained.The results show that the optimal antireflective film thickness varies from 60nm to 62 nm with the thickness of silicon dioxide layer.Similarly,the method can calculate the optimal multilayer antireflective film thicknesses according to the difference solar spectral irradiance distribution in different regions.