Single‐Chamber Deposited Multilayered Parylene Films with Enhanced Visibility and Substrate Adhesion for Protective Device Coating

Poly‐chloro‐para‐xylylene (parylene‐C) coatings are known for their excellent protective properties; however, their high transparency limits the detection of defects or imperfections in the coating itself. The fabrication of parylene films with enhanced light‐scattering properties and limited visible‐light transmission is highly desirable for practical applications. Therefore, multilayered parylene films are synthesized and demonstrated with simultaneously enhanced visibility and substrate adhesion. Multilayered parylene films are deposited using a single‐chamber chemical vapor deposition process. By adjusting the pyrolysis temperature during parylene deposition, transparent and semi‐transparent/hazy multilayered structures with controlled dimer‐to‐monomer ratios are formed. Optical and morphological analyses reveal that the transparency of multilayered parylene films depends on their surface roughness, thickness, dimer crystallinity, internal refractive index contrast, and void distribution. Both simulation and experimental results demonstrate that the fabricated multilayered parylene films can increase the light extraction efficiency of OLEDs by up to 36% without requiring complex fabrication steps. This work introduces a process that achieves multilayer structures with tunable visibility and enhanced adhesion, all within a single‐chamber system, offering a practical route toward enhancing the optical performance of OLEDs and other optoelectronic devices.