Sprecher
Beschreibung
The advancement of renewable energies is crucial in an age in which we are confronted with growing climate and environmental challenges. Solar energy is considered a highly promising, efficient and environmentally friendly source of energy. However, solar panels lose a significant amount of efficiency due to soiling [1]. Thus, a lot of water (more than 35 billion liters per year) is required to keep the panels clean [2]. Hydrophobic coatings that reduce water consumption by promoting self-cleaning via natural rainfall are of high interest. Further desired properties for solar panel coatings are high transparency and mechanical robustness. Our approach is to prepare a hydrophobic, transparent and mechanically stable prototype material by a sol-gel process based on tetraethyl orthosilicate (TEOS) and an alkyl trimethoxysilane (alkylTMS). Here, we vary the alkyl chain lengths (methyl, propyl and hexyl) and precursors’ solid weight ratios. The resulting coatings have a transparency of around 90%, comparable to those of plain glass. With increasing alkyl chain length and concentration, we obtain increasing hydrophobicity with contact angles higher than 90° and hysteresis of around 10°. For the evaluation of self-cleaning features, scanning drop friction force microscopy (sDoFFI) was utilized. Here, lower drop friction force correlates to better self-cleaning properties. Drop friction decreased with increasing alkyl chain length and concentration. For fixed methylTMS/TEOS and hexylTMS/TEOS ratios, a respective average friction force of 41±2 µN and 23±2 µN was observed at a drop volume of 5 µL. Moreover, this technique enables the characterization of coating homogeneity. A thoroughly uniform frictional force was observed on the respective surfaces (Figure 1). Our methods thus enable the production of transparent, uniform and hydrophobic surfaces whose suitability as solar cell coatings can be investigated by sDoFFI.
[1] Chandler, D. L. (2022, March 15), This is how solar panels can be kept clean - without using water. Weforum. Retrieved June 20, 2024, from https://www.weforum.org/agenda/2022/03/solar-panels-waterless-clean/
[2] (a) Borah et al., Sustainability 2023, 15, 16669. (b) Najmi et al., Energies 2023, 16, 7960.