Flexible PDMS/Al<sub>2</sub>O<sub>3</sub> Nanolaminates for the Encapsulation of Blue OLEDs
Yun Li, Yingfei Xiong, Weiran Cao, Qianqian Zhu, Yanyan Fang, Yinghao Zhang, Mengjia Liu, Fan Yang, Kun Cao, Rong Chen
Abstract
Abstract In this work, the polydimethylsiloxane (PDMS)/Al 2 O 3 nanolaminates with optimized sublayer thickness and interfaces have been developed to protect the organic light‐emitting didoes (OLEDs) from the erosion of the moisture in the ambient. The O 2 plasma pretreatment is used to tune the wettability of the ultrathin PDMS sublayers with nanoscale thickness, and the distinct interfaces between the Al 2 O 3 and PDMS sublayers are obtained. The electrical calcium test is exploited to evaluate the barrier properties of the encapsulation nanolayers, and the water vapor transmission rate (WVTR) value of the 2.5 PDMS/Al 2 O 3 dyads can reach the range of ≈10 −5 g m −2 day −1 . The mechanical stability of the nanolaminates is further improved by introducing the top epoxy layer, which helps move the neutral axis (NA) to the center of the barrier, and the applied external strain decreases significantly. Compared with the sample without the epoxy layer, a slighter increase of the WVTR value of the multilayered encapsulation films with optimized NA position is obtained. Furthermore, the operational lifetime of blue OLEDs encapsulated with the multilayered encapsulation films improves from 6 to more than 370 h, which shows significantly improved stability and reliability.