Polymer Layers by Initiated CVD for Thin Film Gas Barrier Encapsulation

Abstract

In this chapter a thorough description of the initiated chemical vapor deposition (iCVD) process will be given, concentrating on molecular weight and deposition rate of the deposited polymer, which are essential for largescale application in hybrid gas barriers. Practical applications of coatings by iCVD are addressed, and it will be shown that iCVD single layers can be used individually as gas barriers. However, so far the intrinsic moisture barrier function of polymers is too low to meet the strict requirements that are needed for organic light emitting diodes (OLEDs) and organic solar cells. Ultra-high gas barriers, with a WVTR « 103 g/m2/day, are an interesting area for the application of iCVD layers as well; thin polymer layers can be used as defect decoupling layers in multilayer hybrid organic/inorganic gas barriers. Although thin inorganic layers can be very impermeable, they inevitably contain defect or pinholes, through which moisture can permeate. Since these defects tend to propagate through the entire inorganic layer, an intermediate layer is necessary to decouple defects in consecutive inorganic layers. To be able to optimally fulfill their function in such a hybrid multilayer, there are certain required properties for the iCVD layers concerning their smoothness, stability, glass transition temperature and adhesion, which will be discussed. Actual multilayers containing polymer layers by iCVD developed in the groups of Prof. Gleason at MIT and Prof. Schropp at Utrecht University will be addressed, as well as scaling up of the iCVD process, and consequently commercialization.