Preparation and characterization of Superhydrophilic TiO2-SiO2 films for double-layer broadband antireflective coating

A double-layer broadband antireflective coating with remarkable optical performance and superhydrophilicity has been designed and prepared based on TiO₂-SiO₂ hybrid films. The synthesis of TiO₂-SiO₂ composite sols is carried out using titanium isopropoxide and tetraethyl orthosilicate as raw ingredients in an acid-catalyzed system. The TiO₂-SiO₂ hybrid film with refractive index of 1.61 (at 550 nm) is used as the bottom layer, and the other mesoporous TiO₂-SiO₂ film templated by an ethylene oxide-propylene oxide-ethylene oxide triblock copolymer is employed as the top layer to achieve the design concept of quarter-half structure. The average transmittance reaches 99.17% in the visible spectral range. The water contact angle of the coating is observed to reduce significantly from 47° to 9.75° by introducing ammonia treatment, indicating that the double-layer coating exhibits superhydrophilicity. Simultaneously, due to the doping of TiO₂, the double-layer coating possesses a high abrasion resistance. The prepared double-layer antireflective coating has potential application in various areas, like solar cells, eyeglasses and windows of high-rise buildings, etc.