Visible detection of performance controlling pinholes in silica encapsulation films

Abstract

For the first time in atmospheric pressure-plasma enhanced chemical vapour deposition of amorphous silica onto flexible polymer substrates, pinholes have been visibly detected using interferometric microscopy and their average diameter of 1.7 μm calculated. Pinholes were found to control the water vapour transmission rate of all 30 nm films deposited with input energies greater than 9 keV per precursor molecule, thus presenting an opportunity for the synthesis of single layer thin films with precisely targeted permeation rates. The pinholes themselves were understood to originate from interactions between the polymer substrate and filaments in the plasma. The non-uniformity of the discharge was attributed to the reduced concentrations of precursor tetraethyl orthosilicate and oxygen species necessary to deposit amorphous silica at high specific energies.

Open-Air Plasma-Deposited Multilayer Thin-Film Moisture Barriers

“…Multilayer thin-film barrier structures offer significant advantages compared to single layers yet retain compatibility with flexible devices . Alternating layers of inorganic and organic layers lead to synergistic effects: the inorganic layer effectively blocks moisture or oxygen, and the organic layer passivates defects such as pinholes in the inorganic layer while also smoothing out roughness on underlying layers. − As a result, multilayer structures demonstrate more impressive barrier properties and have achieved a 15× reduction in the oxygen transmission rate for OLED devices. Recent work has applied the multilayer barrier concept to perovskite solar cells. − In one example, a combination of aluminum-doped zinc oxide and atomic layer-deposited (ALD) tin oxide led to 350 h stability in ambient lab air conditions .…”