Adherent Antireflection Coatings On Borosilicate Glass For Solar Collectors

Borosilicate glass tubes as parts of parabolic-trough solar collectors reflect a total of ~8% of the incident sun light, thus reducing greatly the efficiency of solar power installations. This paper describes the successful development of a porous SiO2-containing antireflective coating ~110 nm thick, which was applied by a sol-gel dip coating process & which increased the light transmittance by up to 5%. Previous antireflective coatings did not have sufficient adhesion strength & resistance to wiping on borosilicate glass, so that they do not withstand the rough operating conditions seen in practice. The essential component enhancing the stability of the coating turned out to be H3PO4 which is added to the dipping solution.