Thin-film encapsulation of top-emission organic light-emitting devices with polyurea/Al2O3 hybrid multi-layers

We developed a room-temperature encapsulation process based on multi-stack of ultra thin Al2O3 and polyurea layers for top-emission organic light-emitting devices (TEOLEDs). Device structure, including a capping layer for refractive-index matching and a thick polyurea buffer layer, was optimized to enhance light extraction without distorting electroluminescence spectrum. The efficiency of a TEOLED encapsulated with 5 pairs of Al2O3(50 nm)/polyurea(20 nm) layers was better than that of a glass-encapsulated TEOLED, whereas their color coordinates were almost identical. Moreover, the half-decay lifetime of a TEOLED encapsulated with 5 pairs of Al2O3/polyurea layers was 86% of that of a glass-encapsulated TEOLED. Water vapor transition rate of 5 pairs of Al2O3(50 nm)/polyurea(20 nm) layers on PET film was measured as low as 5 x 10(-4) g/m(2) day. (C) 2009 Elsevier B.V. All rights reserved.