A Study of Mechanical and Water Vapor barrier Performances for Flexible organic Solar Cells Protecting Coating

摘要

The combination of a hard and brittle silica-like layer (SiO_x) with a soft organosilicon layer (SiO_xC_yH_z) depositing on PET substrate by PECVD and initiated-PECVD respectively, leads to a good protective coating for OPV modules. While the inorganic layer exhibits barrier properties, the organic layer enables a reduction of the defects in the upper inorganic layer as well as an enhancement of the mechanical properties of the stack barrier. A 100-nm-thick silica-like layer shows fracture flexibility at relatively small radius of curvature about 5.5 mm under tension and about 2 mm under compression. The critical tension bending fracture value was further decreased to less than 1.5 mm by reducing layer thickness to 30 nm. Flexibility failure of the 100-nm-thick silica-like layer placed under tension was enhanced when deposited over the smooth and soft organosilicon layer. In that case, the critical bending radius of this layer was about 4 mm instead of 5.5 mm. Besides, tensile fragmentation test revealed high coating cohesion and adhesion related to high coating durability. SiO_xC_yH_z/SiO_x dyad exhibited a transparency of about 92-93% in the wavelength range of 400-800 nm which fulfills the transmittance requirement for an OPV module. Regarding barrier performance, the WVTR of a single silica-like layer deposition decreases from in the range 0.1 to 0.02 g/m~2/day 1 at 25°C and 85% RH when the thickness increases from 50 to 100 nm. WVTR of 0.02 g/m~2/day 1 was also obtained by depositing only 20 nm thick SiO_x layer over a 1μm-thick SiO_xC_yH_z layers, which improved barrier mechanical properties.