Preliminary studies of effects of surface morphology and chemistry of silica-based antireflection coatings on anti-soiling performance under Ningbo’s climate

Abstract

Silica-based antireflection coatings (ARCs) used in photovoltaic (PV) modules often encounter soiling problems, which has been recognized as one of the most serious problems degrading the power output of PV modules. In this work, four kinds of silica-based ARCs were prepared to investigate the effects of surface morphology and chemistry on their anti-soiling properties under Ningbo’s climate. To reveal the influences of surface morphology, hollow silica nanoparticle (HSN)- and solid silica nanoparticle (SSN)-based ARCs were prepared and compared. To understand the surface chemical effects, we comparatively studied the soiling behavior of hydrophilic and hydrophobic HSN ARCs postmodified with methyl and fluorinated groups (named CH3-HSN and F-HSN, respectively). After half-year field tests, we found that the HSN ARCs with a rougher surface exhibited better anti-soiling performance than the SSN ARCs. On the other hand, the hydrophilic ARCs showed better soiling resistance than the hydrophobic controls because of the role of rain cleaning in the soiling mitigation of the hydrophilic samples installed at a moderate tilt angle under a typical coastal climate. Comparing the hydrophobic samples modified with methyl and fluorinated groups, the former was superior to the latter in both laboratory and outdoor tests because of the larger adhesion force between contaminants and the surface in the fluorinated-HSN ARCs. These findings provide constructive guidance for the applications of silica-based ARCs in PV modules installed in coastal areas, which is the key to maximizing the power output of PV modules in practice.