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 degrees to 9.75 degrees 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. Highlights 1. Due to the doping of TiO2, the double-layer coating possesses a high abrasion resistance. 2. The ammonia treatment step not only increases the transmittance of the film but also increases the hydrophilicity of the film. 3. The high transmittance and the superhydrophilicity endow the coating with great potential for practical applications.