UV curable hydrophobic inorganic-organic hybrid coating on solar cell covers for photocatalytic self cleaning application

A process for obtaining a low temperature, UV curable inorganic-organic hybrid coating having excellent photoactive properties which is suitable for glass surfaces such as solar cell covers, automobile rear view mirrors and several electronic devices is presented. Nano titania sol having an average particle size of 19 nm has been synthesized using the aqueous sol-gel route starting from titanyl sulphate and was made highly photoactive by crystallizing through a simple microwave treatment which is of considerable importance in the synthesis of hybrid coatings where conventional heat treatment is not possible. The photoactive titania particles were then partially covered by silica particles by optimizing the amount of the silane moiety. A multifunctional monomer composition was further prepared and coated on a solar cell cover glass followed by a second layer coating using photoactive titania particles by dip coating and was cured under UV for six hours. The coated substrate shows photocatalytic efficiency as well as transparency >90% and further, a water contact angle >90 degrees. Titania particles were uniformly distributed on the surface of the top coating as revealed by AFM and the coating had a total thickness of approximately 2.5 mu m. The appropriate ratio of organic silanes/acrylates imparts strong adhesion to the substrate, while the inorganic components composed of a hybrid mixture of silica/titania enhanced the self cleaning efficiency. Such multifunctional coatings on solar cell covers have considerable advantage in preventing surface contamination from the exposed atmosphere which decreases the efficiency of such panels in the 15-25% range.