Abstract
The water vapor transmission rate (WVTR) of a gas barrier coating is a critically important parameter for flexible organic device packaging, but its accurate measurement without mechanical stress to ultrathin films has been a significant challenge in instrumental analysis. At the current stage, no reliable results have been reported in the range of 10−6 g m−2 day−1 that is required for organic light emitting diodes (OLEDs). In this article, we describe a solution for this difficult, but important measurement, involving enhanced sensitivity by a cold trap, stabilized temperature system, pumped sealing and calibration by a standard conductance element.
Highlights
The water vapor transmission rate (WVTR) of a gas barrier coating is a critically important parameter for flexible organic device packaging, but its accurate measurement without mechanical stress to ultrathin films has been a significant challenge in instrumental analysis
The de facto standard of the WVTR measurement is evaluating the corrosion of an encapsulated calcium metal thin film[6,7,8], but it requires very a long time ranging from weeks to months
The measuring system mainly consists of a sample chamber, which is equipped with a water container, a reservoir, a cold trap, and a measuring chamber, which is equipped with a quadruple mass spectrometer (QMS) (Fig. 2)
Summary
The measuring system mainly consists of a sample chamber, which is equipped with a water container, a reservoir, a cold trap, and a measuring chamber, which is equipped with a quadruple mass spectrometer (QMS) (Fig. 2). The sample chamber has a outer hull to pump out This is necessary to prevent the water vapor from the wet side or in the atmosphere to diffuse into the dry side through the o-ring. The temperature of the cold trap was decreased to 77 K to trap the H2O molecules During this operation, the H2O vapor keeps permeating through the sample and is accumulated in the sample space. The quantity of permeated water vapor during the accumulation time can be obtained using the QMS signals and flow rate sensitivity. We used the SCE to evaluate the accuracy of the measurement by connecting it to the detecting system (including cold trap) in place of the sample chamber. We believe that the present procedure is one of the best at present stage
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