NOVELTY - Preparation of silicon dioxide thin film involves forming rare-earth salt liquid, adding cetyltrimethylammonium bromide, n-heptane and n-hexanol to Erlenmeyer flask, adding solution containing trivalent lanthanum ion, adding sodium fluoride and hydrofluoric acid, adjusting pH, adding to reactor, placing in oven, cooling, adding acetone, separating yttrium-erbium-doped sodium fluoride nanoparticles, dissolving in micelles, adding tetraethyl ortho silicate precursor, adjusting pH using weak acid, adding to silicon dioxide sol conversion material and performing spin-coating method.    USE - Preparation of silicon dioxide thin film for solar cell (claimed).    ADVANTAGE - The method efficiently provides silicon dioxide thin film. The solar cell provided using silicon dioxide thin film has excellent efficiency and reduced performance drop.    DETAILED DESCRIPTION - Preparation of silicon dioxide thin film involves forming rare-earth salt liquid by dissolving yttrium nitrate, ytterbium nitrate and erbium nitrate, adding 1.5 g cetyltrimethylammonium bromide, 8 ml n-heptane and 1000 ~L n-hexanol to Erlenmeyer flask, performing electromagnetic stirring at room temperature for 20 minutes, adding 500 ~L solution containing trivalent lanthanum ion, adding 550 ~L sodium fluoride and 6 ~L hydrofluoric acid, stirring for 30 minutes, adjusting pH to 1.5-3 using acidic solution, standing for 20 minutes, adding to 50 ml stainless steel reactor, placing in oven at 150 degrees C for 4-8 hours, cooling, standing for 12 hours, adding resultant solution to beaker, adding 10 ml acetone, separating yttrium-erbium-doped sodium fluoride nanoparticles, dissolving in micelles, adding tetraethyl ortho silicate precursor, adjusting pH using weak acid, performing electromagnetic stirring, adding to silicon dioxide sol conversion material and performing spin-coating method. The volume ratio of trivalent yttrium ion, trivalent ytterbium ion and trivalent erbium ion is 78:20:2. An INDEPENDENT CLAIM is included for solar cell.