Facile sol-gel synthesis of highly durable anti-reflection films with enhanced self-cleaning performance for perovskite solar cells

Abstract

Conventional antireflective films for solar cells are usually porous for high transmittance, but still suffer from weak weatherability and poor hydrophobicity because water droplets can enter porous films easily and degrade the antireflection performance. In order to achieve a good balance between high transmittance and excellent hydrophobicity, superhydrophobic porous SiO₂ bilayer film with refractive index gradient was designed. Mesoporous SiO₂ film with high refractive index as inner layer was synthesized on the glass at first and then superhydrophobic porous SiO₂ film with low refractive index was prepared by a facile sol-gel method using hexamethyldisilane (HMDS) as modifier. As HMDS content increases, the hydrophobicity of the upper layer was significantly improved while the transmittance was slightly decreased because the -OH on the layer were gradually replaced by -CH₃. When volume ratio of HMDS to Alkali (V_HMDS/Alkali) was 0.6, a large water contact angle (WCA) of 163.6° and high transmittance increase of 2.82% was obtained. When applying this film to the glass on the surface of perovskite solar cells, an obvious increase (0.78%) in photoelectric conversion efficiency (PCE) was obtained. Especially, the superhydrophobic SiO₂ bilayer film exhibited a higher transmittance increase of 3.19% in the broad wavelength range of 380–1100 nm and larger WCA of 161°. In addition, after a 24-h immersion in a water bath at 80 °C, the transmittance was only reduced by 0.26%, indicating a good weatherability. Therefore, this work can provide a more innovative, superior, and facile method to prepare promising antireflection coatings for solar cells.

Graphical Abstract