Synthesis And Modification Of The Nano Antireflective Film For Solar Module Glass

It can improve the generating efficiency of solar cells and shorten the cost recoveryperiod of grid-connected power generation using antireflective solar glass, and thecomprehensive competitiveness of the market is enhanced, so the project has very goodmarket prospect and application value under China’s new energy strategy planningbackground. Nanometer SiO₂antireflection coating solution was prepared by Sol-gel method,porous SiO₂film was coated on the surface of the glass by suitable coating process, then heattreated or toughened, thus the coating and the glass substrate was firmly combined,antireflective glass for solar photovoltaic modules was successfully fabricated with hightransmittance in solar cell’s response spectral range, good weather resistance, high hardnessand good scratch resistant ability.Factors that affecting synthesis of the acid-and base-catalyzed SiO₂sols, includingnH2O/nTEOS, nEtOH/nTEOS, aging time, pH value, et al., were studied systematically usingorthogonal test system firstly, effects on viscosity, particle size, stability of the sols wereanalyzed, and stable sols with controlled particle size were obtained. Film derived fromacid-catalyzed sol was tense and had good scratch resistant ability and high hardness, but theadded transmittance value was limited. Porous membrane with visible light transmittance ofup to98.22%was derived from base-catalyzed sol; however the film had poor wear resistanceand low hardness.When the base-catalyzed sol doped with polysiloxane, macromolecules of entangledlinear or randomly branched chains formed in the acid catalyzed silica sols were introduced,long-chained polysiloxane was filled into the gaps between the spherical particles inbase-catalyzed sol and formed a mutual adhesion，which resulted in the increase of viscosityand improvement of system stability. With the doping ratio increased, porosity of films wasreduced and refractive index increased, the film became denser and smooth, resulting in thedesirable increase of the durability, abrasion resistance and hardness. Refractive index couldbe adjusted from1.23to1.42continuously by changing the doping ratio. When the dopingratio increased from0%to16%, the visible light transmittance of the film declined from97.81%to94.24%quickly, the transmittance attenuation after outdoor exposure for90daysreduced from2.70％to0.22%successfully, and the abrasive-resistance properties of thesilica films improved remarkably. Take all factors into consideration, the films derived frommodified base catalyzed sol with5vol%doping ratio exhibits high transmittance, good weather-resistance and high abrasion-resistance.Antireflective film derived from the base catalyzed sol has low hardness and poormechanical strength. Mechanical properties of the films including hardness, scratch resistanceability had been significantly improved by introducing TiO₂sol, ZrO₂sol and Al₂O₃solutionto modify the base sol, because of the inorganic ceramic oxide filled to the silica networkstructure and acted as good composite reinforcement effect. The hardness of the film could beimproved continuously with the increasing TiO₂, ZrO₂, Al₂O₃doping ratio, but refractiveindex of the film increased, transmittance decreased when adding too much modifiers. Sochoosing suitable adding ratio is quite important, which can maintain the film mechanicalproperties and optical properties.Polysiloxane and nano-TiO₂sol was used to modify the base-catalyzed sol, antireflectivesolar glass with hydrophilic self-cleaning function were prepared. The film’s hardness waspromoted the by amorphous TiO₂nanoparticles as nanometer reinforcing phase, and weatherresistance of the films derived from the modified sols was improved significantly. The filmshad excellent weather resistance, with degradation of transmittance after damp-heat test only0.23％. The adhesion of the film was5B, and pencil hardness of the film could be equal orhigher than3H. The average peak power output of solar module using antireflective glass wasimproved by3.20%than that of uncoated ones.Due to the water absorbed from the surroundings, the transmittance of traditional silicacoatings declines with time. The base-catalyzed sol was modified by the sol derived frommethyl triethoxy silane （MTES） hydrolyzed under acid conditions. The-Si-CH3hydrophobicgroups were successfully introduced into the SiO₂network by means of in situ synthesis, somodified SiO₂sol was prepared with the surface of nano-SiO₂particles having hydrophobiceffect, and then antireflective solar glass with hydrophobic self-cleaning function wereprepared. Infrared spectroscopy analysis showed that hydrophobic methyl was successfullyintroduced to the film structure after doping MTES, with absorption peaks of-OH decreasedand absorption peak of-CH3enhanced, so the active hydroxyl silicone in the networkstructure had been replaced by hydrophobic methyl. Thus, the problem of transmissionattenuation of the films caused by moisture and water absorption was solved successfully.When the volume doping ratio of MTES was40%, the film had high transmittance of96.25%,and high hydrophobicity with contact angle of134.4°.The nanometer antireflective solutions were stable and reliable researched in this project.Durable antireflective glass for solar photovoltaic modules was prepared with transmittance≥94.3%, coating adhesion to5B level and pencil hardness of4H. It was proved by the customer that the peak power of modules using the products was improved by more than2.58%. As theindustry leading level, it has a very good market prospect and promotion value, and can bewidely used in the field of solar photovoltaic.