Deposition of transparent and flexible nanolayer barrier on standard coating materials for photovoltaic devices

Hydrophobic layers are generated and chemisorbed onto standard coating materials for photovoltaic (PV) devices in order to improve their barrier properties against the atmospheric degradation agents and achieve a higher lifetime for the coated devices. The hydrophobic layers are deposited on PET-–SiOx substrates using two different molecules (alkylsilanes and fluoroalkylsilanes) as precursors. High liquid barrier properties are achieved for the fluoroalkylsilane coated PET-–SiOx, best results being average water contact angle > 130° and average oil contact angle > 90°. A chemical mechanism hypothesis is provided in order to explain the different reactive behavior observed for the PET-–SiOx samples with alkylsilanes and fluoroalkylsilanes, respectively. Moreover, the oxygen barrier properties are significantly improved by the fluoroalkylsilane layer deposited in ethanol, that leads to a 70% reduction of the Oxygen Transmission Rate (OTR) compared to that of the uncoated PET-SiOx substrate.