Study Of Light And Thermal Management Based On Ultra-broadband Versatile Textures In Photovoltaic Modules

Increase of operating temperature in photovoltaic(PV)modulesdeteriorates the solar cell photoelectric conversion efficiency and system reliability,therebyaffecting the power output and ending life.In this thesis,we fabricatedultra-broadband versatile textures on the low-iron glass via a modified sol-gel andgraphicimprinting technology,and transferred the pyramidal textures from commercially available crystalline silicon wafers to the glass.Meanwhile,the optical properties,durability and passive radiative cooling were studied and compared.Furthermore,the glass with imprinted textures was applied to PV modules as anencapsulate cover,theshort current density and photoelectric conversion efficiency of solar cell were studied,which realizing the light management and thermal management ofPV modules.The major conclusions were summarized as follows:1.A facile preparation method of hybridized silica sol-gel resistand PDMS soft template was developed for exploring the thermal nano-imprint lithography process,and we try to fabricate the optical disc and the optical grating microstructure.2.TheMicro/nano pyramidal silicatextureand UVtexturetransferred from commercially available crystalline silicon wafers,were prepared respectivelyby using the thermal nano-imprint lithography and UV-imprint lithography.The SEM morphology of silica imprinted pyramidal textures were more regular and uniform than UV sample.The silicatextureand UV texture had a feature sizebetween the Vis-NIR and the MIR wavelengths,which were 1.7μmand 1.9μm,respectively.The average transmittance ofsilica texture at the wavelength from 350 to 750 nm reached 94.7%,much higher than that of 92.3% of the UV texture.In particular,besides the superiority in optical properties,the average transmittance of silica texture was maintained at 100% of the initial value even after the 24 h highly-accelerated temperature and humidity stress test,higher than that of 97.3% of the UV texture.The average transmittance of silica texture decreased slightly,then remained unchanged,while UV texture increased slightly at the wavelength from 300 to 1200 nm.3.It was found that ordinary glass has the strong reflectancepeaks around 8-13μm and 20-30μm,based on the simulation of Maxwell-Garnett effective medium theory,while the ultrawideband nanostructures could obviously suppress the reflectivity of the two spectral regions.According to the experiments,theinfrared emissivity of silica imprinted glass with pyramidal textureswere higher than 0.96 at the atmospheric window between 8 to 13μm.At a solar heat power of 800 W/m2,the temperature of bare silicon could be decreased by 16.39 K using the imprinted texture glass for encapsulation,which showing a good radiation cooling effect.4.The roles of the silica texture glass as an encapsulate cover in silicon PV modules were investigated through photocurrent-voltage(I-V)measurements.It was observed that the incident light was more effectively coupled into the solar cell asthegeometrical optics and combined effect of AR and light trapping from the silica texture glass.The short-circuit current density was improved to 42.08 from 40.03 mA/cm2 with an increase of 5.12% in relative terms.Eventually,the conversion efficiency was increased to 18.12% from 17.57% with an increase of3.13% in relative terms.