The effect of moisture ingress on titania antireflection coatings in field-aged photovoltaic modules

Titanium dioxide (TiO
2
) or titania antireflection coating (ARC) enhances photovoltaic (PV) module efficiency. Yet, degraded TiO
2
can affect the performance reliability of PV modules. In the present work, the effect of moisture ingress on the degradation of TiO
2
ARC in a field-aged multicrystalline silicon PV module is investigated. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analyses show degradation of the TiO
2
ARC. Disintegration of the TiO
2
nanoparticles (NPs) were also observed. The assumed Ti-O stoichiometry of the degraded TiO
2
ARC in the field-aged PV module was found to be higher than 1:2. It turned out that moisture ingress strongly influences the surface morphology and defects, crystallinity, and stoichiometry of TiO
2
ARC in the PV module during field operation. Silver and aluminium NPs migrate to and aggregate on the surfaces of the TiO
2
NPs which might likely lead to the formation of titania-metal complexes such as titania-alumina and silver-titania complexes. These degradation mechanisms affect the opto-electrical properties of the TiO
2
ARC in the PV module.