| AVS 56th International Symposium & Exhibition | |
| Thin Film | Friday Sessions |
| Session TF-FrM |
| Session: | Transparent Electronic Materials and Applications |
| Presenter: | F.J.H. van Assche, TNO Holst Centre, The Netherlands |
| Authors: | F.J.H. van Assche, TNO Holst Centre, The Netherlands E.W.A. Young, TNO Holst Centre, The Netherlands J.J. Michels, TNO Holst Centre, The Netherlands G.H. Rietjens, Philips Research Laboratories, The Netherlands P. van de Weijer, Philips Research Laboratories, The Netherlands P.C.P. Bouten, Philips Research Laboratories, The Netherlands A.M.B. van Mol, TNO Holst Centre, The Netherlands |
| Correspondent: | Click to Email |
A flexible multi-layer ultra-barrier stack consisting of stacked silicon nitride layers interleaved by planarization layers has been developed for encapsulation of OLEDs on foil.
For this purpose a low temperature (<120°C) silicon nitride, deposited using a RF-driven parallel plate plasma reactor, has been optimized both on c-Si and on PEN foil by using spectroscopic ellipsometry (SE) and Fourier transform infrared spectroscopy (FTIR).
However, while intrinsically very low water vapour transmission rates (WVTR <<10-5 g/m2/day at room conditions) of the SiN can be achieved, the total flux of water through the barrier stack is eventually determined by the presence of local defects or pinholes. To gain insight in the transport mechanism of water in the barrier stack, both modelling and a method to trace pinholes in the barrier stack has been applied. On samples (both Ca-mirrors and OLEDs) excellent correspondence of local decay to local presence of water in the barrier stack has been shown.
Ca mirror tests of these barriers on PEN foil have yielded spotless devices after several weeks of accelerated lifetime testing at 60°C and 90% RH and even at 85°C/85% climates. Accelerated lifetime testing at 60°/90% of encapsulated OLEDs resulted in a significant yield of 6 cm2 OLED devices without visible black spots due to cathode oxidation for over 3 weeks in this harsh climate.
Mechanical compatibility of the barrier coating with respect to R2R processing has been verified by means of bending tests of SiN layers on foil. As a next step towards R2R processing of barriers, the feasibility of R2R compatible plasma deposition by means of in-line microwave driven plasma sources is investigated. Barrier layer quality is monitored as a function of deposition rate and thickness.