One step process of decomposition and polymerization to fabricate SiO2 hollow spheres/polyimide composite for foldable OLEDs

Abstract

The fabrication of interlayer dielectrics (ILDs) in flexible organic light-emitting diodes (OLEDs) requires flexible materials with a low dielectric constant as well as materials with excellent electrical, thermal, and mechanical properties for optimal device performance. Hybrid films of SiO2 hollow spheres (SHS)/polyimide (PI) were prepared using a one-step process, with simultaneous occurrence of decomposition (polystyrene, PS) and polymerization (PI) (SODP). No collapse of SiO2 hollow spheres in PI was observed from 10vol% to 60vol% SHS in hybrid films. The dielectric constant of hybrid films was reduced from 3.45 to 1.67 and was saturated at above 50vol% of SHS due to the maximum fill factor of SHS in the PI matrix. The thermal stability was excellent up to 500°C due to the inherent thermal property of PI. After a bending test for 50,000 cycles at a bending radius of 1mm, the SHS/PI hybrid films retained their dielectric constant and current density. These results indicate the hybrid film to be the most promising candidate for flexible ILDs with a low dielectric constant and high thermal stability for foldable OLEDs.