The Preparation And Application Of Antireflective And Near-infrared Luminescent Films For Solar Cells

In this study, the SiO₂nanoparticles and nano-hollow-sphere colloids werefabricated by the easy and convenient sol-gel methods. These two kinds of colloidswere spin-coated on glass substrate as the antireflection films. Near-infraredluminescent YVO₄:Yb³⁺films and SiO₂/YVO₄:0.01Yb³⁺bifunctional films were alsofabricated on glass substrate via sol-gel methods. In addition， the structures,morphologies and optical properties of as-prepared products were characterized byusing X-ray powder diffraction （XRD）, field mission scanning electron microscopy（FESEM）, transmission electron scanning microscopy （TEM）, atomic forcemicroscope （AFM）, UV-Vis-NIR spectrophotometer （UV-Vis-NIR） and fluorescencespectroscopy （PL）, respectively.Here, the effects of the synthesis technics and reaction conditions on thestructure, morphology and optical properties of as-prepared samples have beenstudied. The main results are summarized as following:1) The SiO₂nanoparticles colloids were prepared by easy and convenient sol-gelmethods, nanoporous silica antireflection films were prepared through a simplespin-coated method use polyurethane（PU） as template. According to the TEM andFESEM figures, the as-prepared nanoporous silica antireflection films were flat,smooth and uniform, with nanoporous inside of it. Compared with glass substrate, thetransmittance of nanoporous silica coated glass were significantly increased, themaximum increase is up to3.6%. We also discuss the effects of particle size, filmthickness, porosity on the transmittance of silica nanoporous antireflection films. Thedetailed results indicate: The silica with particle size of8nm had better antireflectionperformance; The transmittance spectrum shift to longer wavelengths with the film thickness increase; The film with higher porosity results higher transmittace.2) The SiO2nano-hollow-sphere colloids were prepared by easy and convenientsol-gel methods use polyacrylic acid（PAA） as template, nano-hollow-sphere silicaantireflection films were prepared through a simple spin-coated method. According tothe TEM, AFM and FESEM figures, the as-prepared silica antireflection films wereflat, smooth and uniform. Compared with glass substrate, the transmittance ofnano-hollow-sphere silica coated glass were significantly increased, the maximumincrease is up to4.3%. We also discuss the effects of particle size, morphology, filmthickness, porosity on the transmittance of silica antireflection films. The detailedresults indicate: The heterogeneity nano-hollow-sphere silica has a broadbandantireflection properties; The transmittance spectrum shift to longer wavelengths withthe film thickness increase; The film with higher porosity results higher transmittace.3) Multifunctional bilayer nanoporous SiO2/YVO4:0.01Yb³⁺films which show bothantireflection and near-infrared down-conversion luminescence was constructed onglass substrate via an easy sol-gel and spin-coating process. The structures,morphologies and optical properties of as-prepared products were thoroughlycharacterized by using XRD, FESEM, TEM, AFM, UV-Vis-NIR spectrophotometerand PL, respectively. The nanoporous SiO₂/YVO₄:0.01Yb³⁺films show thetransmittance ratio increasing about3.7%in the wide wavelength range from500nmto800nm. Under the excitation of320nm UV light, a strong Yb³⁺emission observedin the range from950to1100nm was assigned to the electronic transitions ofYb³⁺:²F_5/2to²F_7/2state. These facile and straightforward methods may be extended toprepare various other phosphors convertors, thus opening ways to fabricate lightcollecting films for C-Si solar cells.