Durability study of transparent and flexible nanolayer barrier for photovoltaic devices

The need of enhancing the protection of photovoltaic (PV) devices from the atmospheric degradation agents is a fundamental issue to be dealt with in order to extend their lifetime. To this aim, a method was developed for generating transparent and hydrophobic layers chemisorbed onto two different flexible substrates, Polyethylene terephthalate - Silicon oxide (PET-SiOx) and Ethylene tetrafluoroethylene - Silicon Oxide (ETFE-SiOx), which are standard coating materials for PV devices. A durability study was performed of the obtained systems through accelerate ageing tests in order to verify the stability and the chemical resistance of the hydrophobic nanolayers by exposing them to several environmental degradation factors: acid and alkaline water solutions, high temperature and relative humidity. The characterization of the hydrophobic, oleophobic and optical properties for the aged systems demonstrated a higher stability of the modified substrates if compared to the pristine samples, with H2O average contact angle of 107° and 96° after about 700 h of damp heat ageing for the nanocoated PETSiOx and ETFESiOx respectively. Furthermore, X-Ray diffraction analysis was performed of the nanocoated and pristine substrates to assess the effect of the ageing on the materials structure.