Towards new multifunctional coatings for organic photovoltaics

• A cost-effective hydrophobization of commercial silica nanoparticles is introduced.
• The nanoparticle solution is easily applicable by spincoating or LS deposition.
• The contact angle above 170° implies excellent superhydrophobicity.
• Enhanced haze factor and wide-angle diffuse scattering in the vis–NIR are detected.
• A more than 6 % improvement on an organic solar cell efficiency is achieved.

A cost-effective procedure for hydrophobization of commercial silica nanoparticles by octadecyltrichlorosilane or trichloro (1H,1H,2H,2H-perfluorooctyl) silane was developed. The functionalized nanoparticle solution could easily be applied on a glass surface by Langmuir-Schaefer deposition or spincoating to create a superhydrophobic surface with the contact angle above 170°. A hydrophobization driven formation of nanoparticle clusters resulted in multiscale hierarchical surface roughness as evidenced by the stylus profilometry and atomic force microscopy. Consequently, optical measurements in the vis-NIR region revealed enhanced forward diffuse scattering and reduced reflectance in a broad interval of the incidence angles. A small sliding angle far below 1° suggests additional coating functionalities such as the self-cleaning and anti-icing. The coating was tested on a front surface of an organic photovoltaic device. A more than 6% enhancement of the photoconversion efficiency comparing with the uncoated device was achieved which may be even larger in real operation conditions considering the air pollution and humidity.