© The Institution of Engineering and Technology
Evaluation of gas permeation properties through barrier layers is important for the development of flexible organic light-emitting devices (FOLEDs). In this reported work, an helium (He) leak detector was used in a novel permeation test for metallic barrier layers. Aluminium (Al) or chromium (Cr) film was deposited as a barrier layer onto a polyethylene terephthalate (PET) substrate using a magnetron sputtering system. For the samples of PET substrates with Al and Cr films at thicknesses of 200 nm, the He pressures were 3.1 × 10−6 and 1.3 × 10−5 Torr, respectively, as measured via He detector testing. The poor permeation blocking by the Cr film was because of microcracks. The He pressure for samples with 1 000 nm thick Al coating and for Al foil (30 μm) showed different values of 3.2 × 10−8 and 1.1 × 10−10 Torr, respectively, which indicated high sensitivity in a low permeation range. The high sensitivity in permeation properties measured by He detector testing reflected the qualities of He that include one of the lightest weights known to science and a very small size. This He detector test will be useful in the development of long-life FOLEDs, as it will aid the measuring of the gas permeation properties of barrier layers that are highly effective in blocking water vapour.
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