Study On Laser Texturization On The Surface Of Solar Glass

Photovoltaic (PV) technology, as a renewable energy technology, is consideredto be the most reliable and effective way to solve the nowadays energy crisis. Manyworks have been done with the aim to enhance the photoelectric conversion efficiency.An indirect way to fulfill the enhancement is to reduce the surface reflection loss andthus improve the solar cells’ absorption of sunlight. On the basis of this method, threekinds of textured anti-reflection relief structures were designed and fabricated on solarglass by means of laser induced backside dry etching (LIBDE) technique.Due to the fact that there is a high transmittance of solar glass in the band ofvisible and infrared light, ultraviolet (UV) lasers such as excimer and high harmoniclasers were mostly applied in the etching of transparent solar glass, the fabricationefficiency by UV lasers, however, was limited by the laser machining system. In thiswork, a laser texturization system to machine on solar glass was established andinvestigated, in which, a1064nm central wavelength ytterbium-doped short-pulsedfiber laser was applied as the irradiation source and solar glasses were successfullyetched by the infrared fiber laser with an assistant absorbing layer. Different fromother studies, the mostly used metallic thin films were substituted by a non-metalliclayer, i. e.1mm thickness alumina wafer (95%Al2O3) with a surface roughness below350nm and alumina powder with a mean particle size of2.071m. Surfacemorphologies of etched sample by LIBDE were measured and examined by means ofscanning electronic microscope (SEM) and3D profiler. Moreover, the surfaceelements after etching were analyzed by Raman spectrometer and Energy DispersiveSpectrometer (EDS). The etching mechanism was interpreted based on the aboveanalysis and relationships between laser parameters and etching process werediscussed. By applying this etching technique, a2.5×2.5cm2square was textured onthe solar glass.Based on the Fresnel reflection coefficient formulas of planar glass in physicaloptics, the reflectance of two micro structures (convex pyramid and cosine pits array)were deduced and calculated. Additionally, the curves were plotted and analyzed by anumerical analytical software, i.e. MATLAB. In accordance with the calculations,ZEMAX was applied into the optical simulation of four different surface structures,and the results shows that all the texturization structures have the potential to decrease the reflectance and therefore raise the incident irradiance of sunlight. Among that, thecosine pits array texturization performs much better than others. As a consequence,anti-reflection samples in three kinds of patterns catalogs were obtained by settingdifferent texturing paths. The mean reflectance of solar glass was reduced to4.3%according to the measurement of UV-VIS-NIR spectrometer.In order to examine the irradiation power management of textured optical microstructures and light propagation characteristics, further analysis were conducted ontheir topographies and diffractive patterns. The laser textured periodical microstructures are verified to be continuous surface-reliefs, which are characterized as thebinary micro optical diffractive structures. On the other hand, the diffractive patternsare determined by the interaction between cosine grating and micro pits in the trench.Binary micro-optical structures of the features have the prospective applications in theinformation optics and maskless micro machining technology.