Soiling of solar panel surfaces reduces energy output and requires freshwater for cleaning. To address this challenge transparent, hydrophobic, and easy-to-clean silica-based coatings have been fabricated. Analysis of these coatings focused mostly on contact angle measurements, while drop mobility and particle adhesion─key factors for efficient soil removal─remain underexplored. To address this gap, here organically modified silicate coatings were synthesized by mixing tetraethyl orthosilicate (TEOS) with alkyl-trimethoxysilanes (alkyl-TMS) of varying alkyl chain lengths (methyl, n-propyl, and n-hexyl) and concentrations. The films showed high optical transparency (92%) and low surface roughness (0.3-1.0 nm). Increasing alkyl-TMS content and chain length increased surface hydrophobicity, leading to advancing contact angles up to 106°. By scanning drop friction microscopy and colloidal probe AFM, we quantified and correlated drop mobility and particle adhesion. A higher alkyl-TMS content led to a reduced drop friction force and reduced particle adhesion, although, mechanical robustness also decreased. Cleaning tests confirmed that coatings with lower friction and adhesion enable more effective soil removal.
Karakaya et al. (2026) studied this question.