Highly impermeable and flexible silica encapsulation films synthesized by sol-gel process

Silica thin films synthesized sol–gel process are proposed as flexible encapsulation materials.A sol–gel process provides a dense and stable amorphous silica structure,yielding an extremely high elastic deformation limit of 4.9%and extremely low water vapor transmission rate(WVTR)of 2.90×10^(−4)g/(m^(2)∙day)at 60℃and relative humidity of 85%.The WVTR is not degraded by cyclic bending deformations for the bending radius corresponding to a tensile strain of 3.3%in the silica encapsulation film,implying that the silica thin film is robust against the formation of pinhole-type defects by cyclic bending deformations.Flexible organic solar cells encapsulated with the silica films operate without degradation in power conversion efficiency for 50,000 bending cycles for a bending radius of 6 mm.