Solution processing of alternating PDMS/SiOx multilayer for encapsulation of organic light emitting diodes

Dilution of spin-coating solution of UV-curable polydimethylsiloxane (PDMS) precursor with decamethylcyclopentasiloxane (D5) is able to reduce thickness of the resulting PDMS layer to ca. 100 nm without changing its quality to allow partial photochemical conversion to dense, crack- and pinhole-free inorganic SiOx upon its exposure to vacuum UV (VUV) light with a high photon energy (λ = 172 nm, Eph = 7.2 eV) within 3 min to achieve a facile formation of a PDMS/SiOx double layer. The process of conversion of PDMS to SiOx is clearly understood as monitored by multiple analytical methods used in this study. Since D5 does not attack the materials used for organic light emitting diodes (OLEDs) and the whole process is carried out without water, O2 and at room temperature, this newly developed all solution-based processing is ideally suited to fabrication of thin film encapsulation (TFE) that can be integrated in roll-to-roll (R2R) manufacturing of flexible thin film organic electronics devices. Preliminary test on the standardized OLED devices confirms the effectiveness of the solution-processed PDMS/SiOx alternating multiple layer as the TFE to extend their lifetime by 6 times under air and relative humidity of 50%.