Janus Silica Microspheres-Reinforced Polymer-Based Composite Encapsulation Films with Enhanced Barrier and Mechanical Properties

Encapsulation materials are of paramount importance for the long-term reliability of electronic devices. However, a critical challenge is the trade-off between achieving an excellent moisture barrier and maintaining mechanical flexibility in such films. Inspired by the lipid bilayer of cell membranes, this study applied partially hydrophobically modified silica microspheres (Janus-SiO 2 ) prepared via a Pickering emulsion method to polymer matrices, thereby yielding multifunctional composite films. The resulting Janus-SiO 2 /PDMS (Polydimethylsiloxane) composite encapsulation film exhibited outstanding overall performance, including a water vapor transmission rate (WVTR) of 42 g/(m 2 ·day), representing a 71% reduction compared to pure PDMS. This improvement is attributed to the higher crystallinity and reduced free volume of the composite film. Furthermore, the film achieved a tensile strength of 3.53 MPa while maintaining an elongation at break of 315%. In the hydrophilic poly(vinyl alcohol) (PVA) system, the introduction of Janus-SiO 2 similarly endowed the composite film with optimal barrier and water-resistant properties, confirming the broad applicability of this interfacial engineering strategy across polymers with different properties. The composite films are used to enable the stable operation of solar cells under high-humidity conditions. This work elucidates the mechanism by which Janus-SiO 2 enhances multifunctional properties through interfacial design and structural control, offering valuable insights for developing next-generation, polymer-based composite encapsulation materials.